Report better errors when a project revision is invalid

If a manifest specifies an invalid revision property, give the
user a better error message detaling the problem, instead of an
ugly Python traceback with a strange Git error message.

Bug: REPO-2
Signed-off-by: Shawn O. Pearce <sop@google.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/error.py b/error.py
index 029e1227..6b9dff44 100644
--- a/error.py
+++ b/error.py
@@ -17,6 +17,10 @@ class ManifestParseError(Exception):
   """Failed to parse the manifest file.
   """
 
+class ManifestInvalidRevisionError(Exception):
+  """The revision value in a project is incorrect.
+  """
+
 class EditorError(Exception):
   """Unspecified error from the user's text editor.
   """