Only autodetect morphology when result is 404baserock/richardmaw/bugfix/http-fail

The MorphologyFactory class will use a RemoteRepoCache to see if a
morphology file exists, and if it doesn't, uses a file listing to see
if it can detect what build-system is uses, hence what the default
morphology should be.

However, it was overly generic in what error cases it would accept as
the morphology not being found, so if the RemoteRepoCache was suddenly
un-resolvable for a brief period, then it would assume the morphology
didn't exist, and use the default one.

This happened to a user, and the result was a full rebuild.

So we now fix this by only raising the exception that means the file
didn't exist, if we got a HTTP 404.

1 files changed, 5 insertions, 3 deletions

diff --git a/morphlib/remoterepocache.py b/morphlib/remoterepocache.py
index b1544b03..004ba86e 100644
--- a/morphlib/remoterepocache.py
+++ b/morphlib/remoterepocache.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2012-2013  Codethink Limited
+# Copyright (C) 2012-2014  Codethink Limited
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -63,9 +63,11 @@ class RemoteRepoCache(object):
         repo_url = self._resolver.pull_url(repo_name)
         try:
             return self._cat_file_for_repo_url(repo_url, ref, filename)
-        except BaseException, e:
+        except urllib2.HTTPError as e:
             logging.error('Caught exception: %s' % str(e))
-            raise CatFileError(repo_name, ref, filename)
+            if e.code == 404:
+                raise CatFileError(repo_name, ref, filename)
+            raise # pragma: no cover
 
     def ls_tree(self, repo_name, ref):
         repo_url = self._resolver.pull_url(repo_name)