Rename retcode to returncode to be consistent with subprocess.

Change CheckCallError to inherit from Error. This will simplify try/except changes.

TEST=none
BUG=none

Review URL: http://codereview.chromium.org/3324007

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@58695 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/gclient_utils.py b/gclient_utils.py
index 7558b42..cf2cede 100644
--- a/gclient_utils.py
+++ b/gclient_utils.py
@@ -27,13 +27,19 @@
 import xml.parsers.expat
 
 
-class CheckCallError(OSError):
+class Error(Exception):
+  """gclient exception class."""
+  pass
+
+
+class CheckCallError(OSError, Error):
   """CheckCall() returned non-0."""
-  def __init__(self, command, cwd, retcode, stdout, stderr=None):
-    OSError.__init__(self, command, cwd, retcode, stdout, stderr)
+  def __init__(self, command, cwd, returncode, stdout, stderr=None):
+    OSError.__init__(self, command, cwd, returncode, stdout, stderr)
+    Error.__init__(self)
     self.command = command
     self.cwd = cwd
-    self.retcode = retcode
+    self.returncode = returncode
     self.stdout = stdout
     self.stderr = stderr
 
@@ -111,12 +117,6 @@
   return child_nodes[0].getAttribute(attribute_name)
 
 
-class Error(Exception):
-  """gclient exception class."""
-  # TODO(maruel): Merge with CheckCallError.
-  pass
-
-
 def SyntaxErrorToError(filename, e):
   """Raises a gclient_utils.Error exception with the human readable message"""
   try: