project: have clone.bundle failures print better diagnostics

Bug: https://crbug.com/1061473

Change-Id: If066dc56ca575720bfb25c1a9892dbd6f4af15c6
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/261852
Tested-by: George Engelbrecht <engeg@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

project.py

@@ -2676,7 +2676,9 @@ class Project(object):
         # returned another error with the HTTP error code being 400 or above.
         # This return code only appears if -f, --fail is used.
         if verbose:
-          print('Server does not provide clone.bundle; ignoring.')
+          print('%s: Unable to retrieve clone.bundle; ignoring.' % self.name)
+          if output:
+            print('Curl output:\n%s', % output)
         return False
       elif curlret and not verbose and output:
         print('%s' % output, file=sys.stderr)