webkitpy: Make all regex strings use raw string literals.

third_party/WebKit/Tools/Scripts/webkitpy/style/patchreader.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 # Copyright (C) 2010 Chris Jerdonek (chris.jerdonek@gmail.com)
 # Copyright (C) 2010 ProFUSION embedded systems
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 47 matching lines @@
         patch_files = DiffParser(patch_string.splitlines()).files
 
         # If the user uses git, checking subversion config file only once is enough.
         call_only_once = True
 
         for path, diff_file in patch_files.iteritems():
             line_numbers = diff_file.added_or_modified_line_numbers()
             _log.debug('Found %s new or modified lines in: %s', len(line_numbers), path)
 
             if not line_numbers:
-                match = re.search("\s*png$", path)
+                match = re.search(r"\s*png$", path)
                 if match and fs.exists(path):
                     if call_only_once:
                         self._text_file_reader.process_file(file_path=path, line_numbers=None)
                         cwd = FileSystem().getcwd()
                         detection = SCMDetector(fs, Executive()).detect_scm_system(cwd)
                         if detection.display_name() == "git":
                             call_only_once = False
                     continue
                 # Don't check files which contain only deleted lines
                 # as they can never add style errors. However, mark them as
                 # processed so that we count up number of such files.
                 self._text_file_reader.count_delete_only_file()
                 continue
 
             self._text_file_reader.process_file(file_path=path, line_numbers=line_numbers)