Added handling of wikis that have been removed

  Previously the wikis that we have on disk were attempted to be fetched
  regardless of if the wiki was avaliable or not so now we do an explicit
  check to ensure that in the case of a deleted wiki, we do not break the
  whole process.

  Edit: Same fetch check has been added to source repos as well

update_repos

@@ -22,6 +22,7 @@ GIT_CLONE_CMD = 'git clone %s %s %s'
 GIT_CLONE_API_URL = 'https://%s@github.com/%s'
 GIT_SHA_CMD = 'git rev-parse --short %s'
 GIT_FETCH_CMD = 'git fetch'
+GIT_CHECK_REMOTE_CMD = 'git ls-remote'
 
 USER_DETAILS_PATH = '/users/%s'
 
@@ -166,10 +167,22 @@ class CodeRepo(object):
         print("- " + get_color_str(branch, Color.GREEN) + " @ " \
                 + self.get_sha_str(branch, directory) + ' ..'),
 
-    def update(self):
+    def update(self, fatal_remote_errors = True):
         if self.try_clone(False):
             return
 
+        # Check if the remote is still there before fetching
+        return_code = system_exec(GIT_CHECK_REMOTE_CMD, self.target_directory, show_output=False, ignore_error=True).return_code
+        if return_code != 0:
+            # Is it fatal?
+            if fatal_remote_errors:
+                error_message = get_color_str("ERROR: Repo for %s seems to have been deleted. Skipping update." % self.full_name, Color.RED)
+                print error_message
+                raise Exception(error_message)
+            else:
+                print get_color_str("WARNING: Repo for %s seems to have been deleted. Skipping update." % self.full_name, Color.GREEN)
+                return
+
         self.print_start_sha(self.default_branch, self.target_directory)
         system_exec(GIT_FETCH_CMD, self.target_directory, False)
         print self.get_sha_str(self.default_branch, self.target_directory)
@@ -200,6 +213,9 @@ class WikiRepo(CodeRepo):
         # GitRepo clone code, but allow it to fail.
         return CodeRepo.try_clone(self, True)
 
+    def update(self):
+        super(WikiRepo, self).update(fatal_remote_errors = False)
+
 class JsonRepo(object):
     def __init__(self, gh_repo, api_url, config, content=None):
         self.config = config