_linkify_emails_regex = re.compile(r"([a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*)@((?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)", re.I)

In [2]: text._linkify_emails_regex.search('"Ken Mitton" <foobar@gmail.com>').group()
Out[2]: 'foobar@gmail.com'

In [3]: text._linkify_emails_regex.search('"Ken Mitton" <foobar.@gmail.com>').group()
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<type 'exceptions.AttributeError'>        Traceback (most recent call last)

/nail/home/derwiki/pg/yelp-main/<ipython console> in <module>()

<type 'exceptions.AttributeError'>: 'NoneType' object has no attribute 'group'