hgext3rd/__init__.py

templater: add exception-raising version of open_template()

I'm about to add another caller of `open_template()` (in the template
loader). That caller will want to get exceptions instead of `(None,
None)` if the template doesn't exist. This patch therefore changes
`open_template()` to raise exceptions and adds a new
`try_open_template()` that returns the `(None, None)` value.

Differential Revision: https://phab.mercurial-scm.org/D8905

# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil

__path__ = pkgutil.extend_path(__path__, __name__)