Fix lint errors in owners file.

owners.py

 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """A database of OWNERS files."""
 
 import collections
 import re
 
 
 # If this is present by itself on a line, this means that everyone can review.
 EVERYONE = '*'
 
 
 # Recognizes 'X@Y' email addresses. Very simplistic.
 BASIC_EMAIL_REGEXP = r'^[\w\-\+\%\.]+\@[\w\-\+\%\.]+$'
 
 
+def _assert_is_collection(obj):
+  assert (isinstance(obj, collections.Iterable) and
+          isinstance(obj, collections.Sized) and
+          not isinstance(obj, basestring))
+
+
 class SyntaxErrorInOwnersFile(Exception):
   def __init__(self, path, lineno, msg):
     super(SyntaxErrorInOwnersFile, self).__init__((path, lineno, msg))
     self.path = path
     self.lineno = lineno
     self.msg = msg
 
   def __str__(self):
     return "%s:%d syntax error: %s" % (self.path, self.lineno, self.msg)
 
@@ skipping 54 matching lines @@
 
     self._load_data_needed_for(files)
     files_by_dir = self._files_by_dir(files)
     covered_dirs = self._dirs_covered_by(reviewers)
     uncovered_files = []
     for d, files_in_d in files_by_dir.iteritems():
       if not self._is_dir_covered_by(d, covered_dirs):
         uncovered_files.extend(files_in_d)
     return set(uncovered_files)
 
-  def _check_collection(self, obj):
-    assert (isinstance(obj, collections.Iterable) and
-            isinstance(obj, collections.Sized) and
-            not isinstance(obj, basestring))
-
   def _check_paths(self, files):
     def _is_under(f, pfx):
       return self.os_path.abspath(self.os_path.join(pfx, f)).startswith(pfx)
-    self._check_collection(files)
+    _assert_is_collection(files)
     assert all(_is_under(f, self.os_path.abspath(self.root)) for f in files)
 
   def _check_reviewers(self, reviewers):
-    self._check_collection(reviewers)
+    _assert_is_collection(reviewers)
     assert all(self.email_regexp.match(r) for r in reviewers)
 
   def _files_by_dir(self, files):
     dirs = {}
     for f in files:
       dirs.setdefault(self.os_path.dirname(f), []).append(f)
     return dirs
 
   def _dirs_covered_by(self, reviewers):
     dirs = self.owned_by[EVERYONE]
@@ skipping 49 matching lines @@
     # short combinations of owners.
     every_owner = set()
     for f in files:
       dirname = self.os_path.dirname(f)
       while dirname in self.owners_for:
         every_owner |= self.owners_for[dirname]
         if self._stop_looking(dirname):
           break
         dirname = self.os_path.dirname(dirname)
     return every_owner