Back in Python 2.6 timeframe, e-mail multi-line headers used a

continuation character of \t for subsequent lines, which was

problematic on some e-mail clients. Python 2.7 changed this to a space

character (https://bugs.python.org/issue1974).
Since this impacted our users

(https://hellosplat.com/s/beanbag/tickets/3613/), we monkey-patched the

continuation character for Python 2.6 installs.
Unfortunately, this later broke Python 3, as the character was a byte

string, and Python 3 expected to be dealing with Unicode strings. It

wasn't really a problem unless the subsequent lines contained Unicode

characters, which would trip a particular code path in the

email.header.
We no longer support Python 2.6, and have no reason to maintain this

fix, as our injected character has been the default for a long time.

This removes that code entirely, fixing this issue and delegating purely

to Python e-mail code.

Generated some e-mails with long headers that contained Unicode, and

verified the issue along with the fix.
Unit tests were not added, as they'd just be testing the default

behavior/absense of our monkey-patched code, and aren't particularly

useful for any future regression testing (since we're not in charge

of Python's email module).