Handle pygit2.discover_repository() returning None.

A breaking change was made in pygit2 0.27.1: it now returns None
instead of raising a KeyError if the specified path is not in
a Git repository.

Author: ppentchev

gitless/core.py

@@ -58,6 +58,13 @@ class PathIsDirectoryError(ValueError): pass
 GL_STATUS_IGNORED = 3
 
 
+def error_on_none(path):
+  """Raise a KeyError if the ```path``` argument is None."""
+  if path is None:
+    raise KeyError('path')
+  return path
+
+
 def init_repository(url=None):
   """Creates a new Gitless's repository in the cwd.
 
@@ -67,7 +74,7 @@ def init_repository(url=None):
   """
   cwd = os.getcwd()
   try:
-    pygit2.discover_repository(cwd)
+    error_on_none(pygit2.discover_repository(cwd))
     raise GlError('You are already in a Gitless repository')
   except KeyError:  # Expected
     if not url:
@@ -108,7 +115,7 @@ class Repository(object):
   def __init__(self):
     """Create a Repository out of the current working repository."""
     try:
-      path = pygit2.discover_repository(os.getcwd())
+      path = error_on_none(pygit2.discover_repository(os.getcwd()))
     except KeyError:
       raise NotInRepoError('You are not in a Gitless\'s repository')