Gracefully handle ASCII decoding exceptions

[edeca]

Fix #142

[edeca]

Build appears to be failing due to test cases binding ::1 inside Travis.

[waynew]

Hey @edeca can you try this fix - add this to .travis.yaml:

before_script:
  - echo 0 | sudo tee /proc/sys/net/ipv6/conf/all/disable_ipv6

Also it looks like it's missing some code coverage on appveyor:

py35-cov runtests: commands[3] | python -m coverage report -m --rcfile=C:\projects\aiosmtpd/.coverage.ini --fail-under=100
Name                        Stmts   Miss Branch BrPart  Cover   Missing
-----------------------------------------------------------------------
aiosmtpd\__init__.py            0      0      0      0   100%
aiosmtpd\controller.py         50      0      6      0   100%
aiosmtpd\docs\__init__.py       0      0      0      0   100%
aiosmtpd\handlers.py          143      0     50      0   100%
aiosmtpd\lmtp.py               11      0      2      0   100%
aiosmtpd\main.py               74      0     14      0   100%
aiosmtpd\smtp.py              494      6    186      0    99%   239-241, 247-249
-----------------------------------------------------------------------
TOTAL                         772      6    258      0    99%
ERROR: InvocationError for command 'C:\\projects\\aiosmtpd\\.tox\\py35-cov\\Scripts\\python.EXE -m coverage report -m --rcfile=C:\\projects\\aiosmtpd/.coverage.ini --fail-under=100' (exited with code 2)

[edeca]

Test cases now cover both exception handlers and Travis is fixed.

[waynew]

Awesome. AFAICT this looks like a good thing 👍