Get rid of spurious warning about bad --revision flag.

gclient.py

Index: gclient.py
diff --git a/gclient.py b/gclient.py
index bbe6d582b8aaa12e412e8ce3a9eb51288739e0dc..86d45131786521073529607216f830503918ea38 100755
--- a/gclient.py
+++ b/gclient.py
@@ -802,6 +802,7 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
     run_scm = command not in ('runhooks', 'recurse', None)
     parsed_url = self.LateOverride(self.url)
     file_list = [] if not options.nohooks else None
+    revision_override = revision_overrides.pop(self.name, None)
     if run_scm and parsed_url:
       if isinstance(parsed_url, self.FileImpl):
         # Special support for single-file checkout.
@@ -817,7 +818,7 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
       else:
         # Create a shallow copy to mutate revision.
         options = copy.copy(options)
-        options.revision = revision_overrides.pop(self.name, None)
+        options.revision = revision_override
         self.maybeGetParentRevision(
             command, options, parsed_url, self.parent)
         self._used_revision = options.revision