Do not use subprocess to send mail

1 job for split_files in 39 seconds (queued for 1 second)
Name Stage Failure
failed
linters Quality Assurance
cpasswords/client.py:549:1: C901 'edit_file' is too complex (13)
cpasswords/client.py:675:1: C901 'recrypt_files' is too complex (12)
cpasswords/gpg.py:103:1: C901 '_parse_keys' is too complex (19)
ERROR: InvocationError for command /builds/nounous/cranspasswords/.tox/linters/bin/flake8 cpasswords (exited with code 1)
___________________________________ summary ____________________________________
ERROR: linters: commands failed
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1