Add support for Google App Engine dev server

Google App Engine blocks access to many C modules including the
`socket` module. It provides its own implementation but this causes a
`TypeError` when used with the `ssl` module.

Actually import os

Add warning and extra condition

Add support for Google App Engine dev server

Google App Engine blocks access to many C modules including the
`socket` module. It provides its own implementation but this causes a
`TypeError` when used with the `ssl` module. This adds a warning and
skips the SSL check when on in the dev server.