Addressed comment, fixed open-ended except
Addressed comment, fixed open-ended except

Except wile opening a URL now only catches AttributeError, eliminating an issue when
running Python 2 without internet connection.

Eric89GXL/sphinx-gallery,lesteve/sphinx-gallery,sphinx-gallery/sphinx-gallery,Titan-C/sphinx-gallery,Eric89GXL/sphinx-gallery,lesteve/sphinx-gallery,sphinx-gallery/sphinx-gallery,Titan-C/sphinx-gallery