Fix Aphlict logging

Summary:
Yeahhhhhhhh....

• Open a "stream", not a "steam".
• Make error easier for users to understand.
• Write to the log in debug mode so the issue is more apparent.

Test Plan:

• Started server with bad permissions, got usable error message.
• Started server with good permissions, got logfile.

Reviewers: joshuaspence, btrahan

Reviewed By: btrahan

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11339