Resolve proxy_bypass problems.

This resolves the sad, sad 2.6.x problems in `proxy_bypass` as reported in #1844 and #1841.

The nature of this fix is that, fundamentally, we don't care enough to let this call stop us. Assume that if it fails we aren't bypassing the proxy (usually we won't be) and move on with our lives.

I'm only catching the specific exceptions we've seen. I'm open to wrapping this in a generic `except` block if we want to.