This change skips parsing of email addresses where domains include a "@" character, which can be maliciously used since the local part is returned as a complete address. 

(cherry picked from commit 8cb65d13)

Excludes changes to Lib/email/_header_value_parser.py, which did not
exist in 2.7.
Co-authored-by: jpic <jpic@users.noreply.github.com>


https://bugs.python.org/issue34155