[gclient] Short-circut ParseDepsFile if not found

R=gavinmak@google.com

Change-Id: I137105e7766d5de97e62d348d32b31221b5ec43c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5506836
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Auto-Submit: Josip Sokcevic <sokcevic@chromium.org>
Reviewed-by: Gavin Mak <gavinmak@google.com>

gclient.py

@@ -826,10 +826,13 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
             logging.info('ParseDepsFile(%s): No %s file found at %s', self.name,
                          deps_file, filepath)
 
-        if os.path.isfile(filepath):
-            deps_content = gclient_utils.FileRead(filepath)
-            logging.debug('ParseDepsFile(%s) read:\n%s', self.name,
-                          deps_content)
+        if not os.path.isfile(filepath):
+            logging.warning('ParseDepsFile(%s): No DEPS file found', self.name)
+            self.add_dependencies_and_close([], [])
+            return
+
+        deps_content = gclient_utils.FileRead(filepath)
+        logging.debug('ParseDepsFile(%s) read:\n%s', self.name, deps_content)
 
         local_scope = {}
         if deps_content: