Fix subprocess exception name

https://review.openstack.org/227299 added code using
subprocess.CheckedProcessException, which does not exist. From
the Python documentation, it should be
subprocess.CalledProcessError [1]

[1] - https://docs.python.org/2/library/subprocess.html#subprocess.CalledProcessError

Change-Id: I0e03f048a33b1b919e38d22038650a633b8ac5fd

oslosphinx/__init__.py

@@ -28,7 +28,7 @@ def _html_page_context(app, pagename, templatename, context, doctree):
             git_remote = subprocess.check_output(
                 ['git', 'config', '--local', '--get', 'remote.origin.url']
             )
-        except subprocess.CheckedProcessException:
+        except subprocess.CalledProcessError:
             _cgit_link = 'unknown'
         else:
             parsed = urlparse.urlparse(git_remote)