Fix multi-solution use case with conflicting custom_deps overrides.

Let's say there's 2 solutions, solA and solB, both fetching the dependency depA
with different urls, solA has 'depA': 'http://foo/bar' and solB has 'depA':
From('depB', 'bar').

This case used to not work, because LateOverride() was not called in
verify_validity(), so it was not comparing the resolved urls but instead what is
textually specified in both DEPS files.

Also because LateOverride() was not called, verify_validity() was comparing the
original urls even if custom_deps is specified in the solution(s).

Finally, allow one to mismatch the other IFF one is None.

R=szager@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/11088023

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@161228 0039d316-1c4b-4281-b951-d872f2087c98

gclient.py

@@ -325,10 +325,20 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
     # This require a full tree traversal with locks.
     siblings = [d for d in self.root.subtree(False) if d.name == self.name]
     for sibling in siblings:
-      if self.url != sibling.url:
+      self_url = self.LateOverride(self.url)
+      sibling_url = sibling.LateOverride(sibling.url)
+      # Allow to have only one to be None or ''.
+      if self_url != sibling_url and bool(self_url) == bool(sibling_url):
         raise gclient_utils.Error(
-            'Dependency %s specified more than once:\n  %s\nvs\n  %s' %
-            (self.name, sibling.hierarchy(), self.hierarchy()))
+            ('Dependency %s specified more than once:\n'
+            '  %s [%s]\n'
+            'vs\n'
+            '  %s [%s]') % (
+              self.name,
+              sibling.hierarchy(),
+              sibling_url,
+              self.hierarchy(),
+              self_url))
       # In theory we could keep it as a shadow of the other one. In
       # practice, simply ignore it.
       logging.warn('Won\'t process duplicate dependency %s' % sibling)