More verbose output when .gclient file cannot be found

Bug: 773769
Change-Id: I3c1a394c5995e0c56046da5f2509e63060aa6a29
Reviewed-on: https://chromium-review.googlesource.com/712935
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>

gclient.py

@@ -1357,6 +1357,8 @@ it or fix the checkout.
             options.config_filename, os.getcwd()))
       path = gclient_utils.FindGclientRoot(os.getcwd(), options.config_filename)
       if not path:
+        if options.verbose:
+          print('Couldn\'t find configuration file.')
         return None
       client = GClient(path, options)
       client.SetConfig(gclient_utils.FileRead(