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BUG=b:233893248
TEST=CQ

Change-Id: I66591d7a738d241aed3290138c0f68065ab10a6d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3879174
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
diff --git a/api/message_util.py b/api/message_util.py
index 559a888..1f9301b 100644
--- a/api/message_util.py
+++ b/api/message_util.py
@@ -22,7 +22,7 @@
 
 
 if TYPE_CHECKING:
-  from chromite.third_party import google
+    from chromite.third_party import google
 
 FORMAT_BINARY = 1
 FORMAT_JSON = 2
@@ -30,218 +30,238 @@
 
 
 class Error(Exception):
-  """Base error class for the module."""
+    """Base error class for the module."""
 
 
 class InvalidHandlerError(Error):
-  """Raised when a message handler has no input/output argument when needed."""
+    """Raised when a message handler has no input/output argument when needed."""
 
 
 class InvalidInputFileError(Error):
-  """Raised when the input file cannot be read."""
+    """Raised when the input file cannot be read."""
 
 
 class InvalidInputFormatError(Error):
-  """Raised when the passed input protobuf can't be parsed."""
+    """Raised when the passed input protobuf can't be parsed."""
 
 
 class InvalidOutputFileError(Error):
-  """Raised when the output file cannot be written."""
+    """Raised when the output file cannot be written."""
 
 
 class UnknownHandlerError(Error):
-  """Raised when a valid type has not been implemented yet.
+    """Raised when a valid type has not been implemented yet.
 
-  This should only ever be raised when under active development.
-  See: get_message_handler.
-  """
+    This should only ever be raised when under active development.
+    See: get_message_handler.
+    """
 
 
 def get_message_handler(path, msg_format):
-  """Get a message handler to handle the given message format."""
-  assert msg_format in VALID_FORMATS
+    """Get a message handler to handle the given message format."""
+    assert msg_format in VALID_FORMATS
 
-  if msg_format == FORMAT_BINARY:
-    return MessageHandler(
-        path=path,
-        serializer=BinarySerializer(),
-        binary=True,
-        input_arg='--input-binary',
-        output_arg='--output-binary',
-        config_arg='--config-binary')
-  elif msg_format == FORMAT_JSON:
-    return MessageHandler(
-        path=path,
-        serializer=JsonSerializer(),
-        binary=False,
-        input_arg='--input-json',
-        output_arg='--output-json',
-        config_arg='--config-json')
-  else:
-    # Unexpected. Your new format type needs a case in this function if
-    # you got this error.
-    raise UnknownHandlerError('Unknown format type.')
+    if msg_format == FORMAT_BINARY:
+        return MessageHandler(
+            path=path,
+            serializer=BinarySerializer(),
+            binary=True,
+            input_arg="--input-binary",
+            output_arg="--output-binary",
+            config_arg="--config-binary",
+        )
+    elif msg_format == FORMAT_JSON:
+        return MessageHandler(
+            path=path,
+            serializer=JsonSerializer(),
+            binary=False,
+            input_arg="--input-json",
+            output_arg="--output-json",
+            config_arg="--config-json",
+        )
+    else:
+        # Unexpected. Your new format type needs a case in this function if
+        # you got this error.
+        raise UnknownHandlerError("Unknown format type.")
 
 
 class Serializer(object):
-  """Base (and null) serializer class."""
+    """Base (and null) serializer class."""
 
-  def deserialize(self, data: str, message: 'google.protobuf.Message'):
-    """Deserialize the data into the given message.
+    def deserialize(self, data: str, message: "google.protobuf.Message"):
+        """Deserialize the data into the given message.
 
-    Args:
-      data: The message data to deserialize.
-      message: The message to load the data into.
-    """
+        Args:
+          data: The message data to deserialize.
+          message: The message to load the data into.
+        """
 
-  # pylint: disable=unused-argument
-  def serialize(self, message: 'google.protobuf.Message') -> str:
-    """Serialize the message data.
+    # pylint: disable=unused-argument
+    def serialize(self, message: "google.protobuf.Message") -> str:
+        """Serialize the message data.
 
-    Args:
-      message: The message to be serialized.
+        Args:
+          message: The message to be serialized.
 
-    Returns:
-      The message's serialized data.
-    """
-    return ''
+        Returns:
+          The message's serialized data.
+        """
+        return ""
 
 
 class BinarySerializer(Serializer):
-  """Protobuf binary serializer class."""
+    """Protobuf binary serializer class."""
 
-  def deserialize(self, data, message):
-    """Deserialize the data into the given message.
+    def deserialize(self, data, message):
+        """Deserialize the data into the given message.
 
-    See: Serializer.deserialize
-    """
-    message.ParseFromString(data)
+        See: Serializer.deserialize
+        """
+        message.ParseFromString(data)
 
-  def serialize(self, message):
-    """Serialize the message data.
+    def serialize(self, message):
+        """Serialize the message data.
 
-    See: Serializer.serialize
-    """
-    return message.SerializeToString()
+        See: Serializer.serialize
+        """
+        return message.SerializeToString()
 
 
 class JsonSerializer(Serializer):
-  """Protobuf json serializer class."""
+    """Protobuf json serializer class."""
 
-  def deserialize(self, data, message):
-    """Deserialize the data into the given message.
+    def deserialize(self, data, message):
+        """Deserialize the data into the given message.
 
-    See: Serializer.deserialize
-    """
-    try:
-      json_format.Parse(data, message, ignore_unknown_fields=True)
-    except json_format.ParseError as e:
-      raise InvalidInputFormatError('Unable to parse the input json: %s' % e)
+        See: Serializer.deserialize
+        """
+        try:
+            json_format.Parse(data, message, ignore_unknown_fields=True)
+        except json_format.ParseError as e:
+            raise InvalidInputFormatError(
+                "Unable to parse the input json: %s" % e
+            )
 
-  def serialize(self, message):
-    """Serialize the message data.
+    def serialize(self, message):
+        """Serialize the message data.
 
-    See: Serializer.serialize
-    """
-    return json_format.MessageToJson(
-        message, sort_keys=True, use_integers_for_enums=True) or '{}'
+        See: Serializer.serialize
+        """
+        return (
+            json_format.MessageToJson(
+                message, sort_keys=True, use_integers_for_enums=True
+            )
+            or "{}"
+        )
 
 
 class MessageHandler(object):
-  """Class to handle message (de)serialization to and from files.
+    """Class to handle message (de)serialization to and from files.
 
-  The class is fairly tightly coupled to the build api, but we currently have
-  no other projected use cases for this, so it's handy. In particular, if we
-  scrap the "maintain the same input/output/config serialization when reexecing
-  inside the chroot" convention, this implementation is much less useful and
-  can be fairly trivially generalized.
+    The class is fairly tightly coupled to the build api, but we currently have
+    no other projected use cases for this, so it's handy. In particular, if we
+    scrap the "maintain the same input/output/config serialization when reexecing
+    inside the chroot" convention, this implementation is much less useful and
+    can be fairly trivially generalized.
 
-  The instance's path is the primary path the message handler was built for.
-  For the Build API, this means one of the input/output/config arguments. In
-  practice, it's largely a convenience/shortcut so we don't have to either
-  track which input files are what types (which we know from the argument used
-  to pass them in), or create another containing data class for the
-  functionality provided by the handler and serializer classes and the build
-  api data.
+    The instance's path is the primary path the message handler was built for.
+    For the Build API, this means one of the input/output/config arguments. In
+    practice, it's largely a convenience/shortcut so we don't have to either
+    track which input files are what types (which we know from the argument used
+    to pass them in), or create another containing data class for the
+    functionality provided by the handler and serializer classes and the build
+    api data.
 
-  Examples:
-    message_handler = MessageHandler(path, ...)
-    message = ...
-    # Parse path into message.
-    message_handler.read_into(message)
-    # Write message to a different file.
-    message_handler.write_into(message, path=other_path)
-  """
-
-  def __init__(self, path: str, serializer: Serializer, binary: bool,
-               input_arg: str, output_arg: str, config_arg: str):
-    """MessageHandler init.
-
-    Args:
-      path: The path to the main file associated with this handler.
-      serializer: The serializer to be used for the messages.
-      binary: Whether the serialized content is binary.
-      input_arg: The --input-x argument used for this type. Used for
-        reexecution inside the chroot.
-      output_arg: The --output-x argument used for this type. Used for
-        reexecution inside the chroot.
-      config_arg: The --config-x argument used for this type. Used for
-        reexecution inside the chroot.
+    Examples:
+      message_handler = MessageHandler(path, ...)
+      message = ...
+      # Parse path into message.
+      message_handler.read_into(message)
+      # Write message to a different file.
+      message_handler.write_into(message, path=other_path)
     """
-    self.path = path
-    self.serializer = serializer
-    self.read_mode = 'rb' if binary else 'r'
-    self.write_mode = 'wb' if binary else 'w'
-    self.input_arg = input_arg
-    self.output_arg = output_arg
-    self.config_arg = config_arg
 
-  def read_into(self, message: 'google.protobuf.Message',
-                path: Optional[str] = None):
-    """Read a file containing serialized data into a message.
+    def __init__(
+        self,
+        path: str,
+        serializer: Serializer,
+        binary: bool,
+        input_arg: str,
+        output_arg: str,
+        config_arg: str,
+    ):
+        """MessageHandler init.
 
-    Args:
-      message: The message to populate.
-      path: A path to read. Uses the instance's path when not given.
+        Args:
+          path: The path to the main file associated with this handler.
+          serializer: The serializer to be used for the messages.
+          binary: Whether the serialized content is binary.
+          input_arg: The --input-x argument used for this type. Used for
+            reexecution inside the chroot.
+          output_arg: The --output-x argument used for this type. Used for
+            reexecution inside the chroot.
+          config_arg: The --config-x argument used for this type. Used for
+            reexecution inside the chroot.
+        """
+        self.path = path
+        self.serializer = serializer
+        self.read_mode = "rb" if binary else "r"
+        self.write_mode = "wb" if binary else "w"
+        self.input_arg = input_arg
+        self.output_arg = output_arg
+        self.config_arg = config_arg
 
-    Raises:
-      InvalidInputFileError: When a path has not been given, does not exist,
-        or cannot be read.
-    """
-    target_path = path or self.path
-    if not target_path:
-      raise InvalidInputFileError('No input file has been specified.')
-    if not os.path.exists(target_path):
-      raise InvalidInputFileError('The input file does not exist.')
+    def read_into(
+        self, message: "google.protobuf.Message", path: Optional[str] = None
+    ):
+        """Read a file containing serialized data into a message.
 
-    try:
-      content = osutils.ReadFile(target_path, mode=self.read_mode)
-    except IOError as e:
-      raise InvalidInputFileError('Unable to read input file: %s' % e)
+        Args:
+          message: The message to populate.
+          path: A path to read. Uses the instance's path when not given.
 
-    if content:
-      self.serializer.deserialize(content, message)
-    else:
-      logging.warning('No content found in %s to deserialize.', target_path)
+        Raises:
+          InvalidInputFileError: When a path has not been given, does not exist,
+            or cannot be read.
+        """
+        target_path = path or self.path
+        if not target_path:
+            raise InvalidInputFileError("No input file has been specified.")
+        if not os.path.exists(target_path):
+            raise InvalidInputFileError("The input file does not exist.")
 
-  def write_from(self, message: 'google.protobuf.Message',
-                 path: Optional[str] = None):
-    """Write serialized data from the message to a file.
+        try:
+            content = osutils.ReadFile(target_path, mode=self.read_mode)
+        except IOError as e:
+            raise InvalidInputFileError("Unable to read input file: %s" % e)
 
-    Args:
-      message: The message to serialize and persist.
-      path: An optional override of the instance's path.
+        if content:
+            self.serializer.deserialize(content, message)
+        else:
+            logging.warning(
+                "No content found in %s to deserialize.", target_path
+            )
 
-    Raises:
-      InvalidOutputFileError: When no path given, or it cannot be written to.
-    """
-    if not path and not self.path:
-      raise InvalidOutputFileError('No output file has been specified.')
+    def write_from(
+        self, message: "google.protobuf.Message", path: Optional[str] = None
+    ):
+        """Write serialized data from the message to a file.
 
-    try:
-      osutils.WriteFile(
-          path or self.path,
-          self.serializer.serialize(message),
-          mode=self.write_mode)
-    except IOError as e:
-      raise InvalidOutputFileError('Cannot write output file: %s' % e)
+        Args:
+          message: The message to serialize and persist.
+          path: An optional override of the instance's path.
+
+        Raises:
+          InvalidOutputFileError: When no path given, or it cannot be written to.
+        """
+        if not path and not self.path:
+            raise InvalidOutputFileError("No output file has been specified.")
+
+        try:
+            osutils.WriteFile(
+                path or self.path,
+                self.serializer.serialize(message),
+                mode=self.write_mode,
+            )
+        except IOError as e:
+            raise InvalidOutputFileError("Cannot write output file: %s" % e)