file_util.Open: Refactor usages to new module.

Refactor usages from cros_build_lib.Open to file_util.Open.

BUG=b:199404652
TEST=run_tests

Change-Id: Ic7253522351de1d95bf12f78508905309a87b7ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3149419
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Sloan Johnson <sloanjohnson@google.com>
Reviewed-by: Sergey Frolov <sfrolov@google.com>
Commit-Queue: Alex Klein <saklein@chromium.org>
diff --git a/scripts/cros_generate_breakpad_symbols.py b/scripts/cros_generate_breakpad_symbols.py
index 70c4bc7..6fa87a0 100644
--- a/scripts/cros_generate_breakpad_symbols.py
+++ b/scripts/cros_generate_breakpad_symbols.py
@@ -29,6 +29,7 @@
 from chromite.lib import osutils
 from chromite.lib import parallel
 from chromite.lib import signals
+from chromite.utils import file_util
 
 
 SymbolHeader = collections.namedtuple('SymbolHeader',
@@ -52,7 +53,7 @@
   Raises:
     ValueError if the first line of |sym_file| is invalid
   """
-  with cros_build_lib.Open(sym_file, 'rb') as f:
+  with file_util.Open(sym_file, 'rb') as f:
     header = f.readline().decode('utf-8').split()
 
   if header[0] != 'MODULE' or len(header) != 5: