Gracefully handle proxied SyntaxErrors when using the logcapture plugin

Fixes erikrose/nose-progressive#62

The logcapture plugin formats errors by extracting and converting
the value to a string. Nose recreates a proxy exception lacking
filename and lineno attributes, which crashes the shortcut formatting.

This approach just tests for the appropriate attributes and avoids
attempting to create a fancy editor shortcut, while warning the user
they may want to try `--nologcapture` to reveal the full details.