`dkimpy` in Python 3 does not work for 'verify' - AttributeError

[Thomas Ward]

This is fixed in later releases of the `dkimpy` library, specifically tested was 0.6.2 to see if it's fixed.

`dkimpy` in Python 3 on Xenial *does not work* as expected when calling `verify` on a signed message in bytes form. It also fails for 'string' form, because it tries to use bytes patterns on a string object.

This affects 0.5.6-1, but is fixed in Artful and 0.6.2 already. (I'd go version by version to find a fix, but I'm not that concerned since I've already made a backport of `python3-dkim` in a PPA[1].

As this breaks one of the crucial functions (message verification with the `verify` function), I'm setting this as a "High" importance bug.

[1] https://launchpad.net/~teward/+archive/ubuntu/dkimpy-backports

[Thomas Ward (teward)]

When passing a signed message in as bytes to the function in Python 3:

Traceback (most recent call last):
  File "./dmarctests.py", line 45, in <module>
    print("VERIFY: ", dkim.verify(signedmsg))
  File "/usr/lib/python3/dist-packages/dkim/__init__.py", line 630, in verify
    return d.verify(dnsfunc=dnsfunc)
  File "/usr/lib/python3/dist-packages/dkim/__init__.py", line 563, in verify
    s = dnsfunc(name)
  File "/usr/lib/python3/dist-packages/dkim/dnsplug.py", line 84, in get_txt
    txt = txt.encode('utf-8')
AttributeError: 'bytes' object has no attribute 'encode'

[Thomas Ward (teward)]

When passing a signed message in as a UTF-8 string (decoded from bytes):

Traceback (most recent call last):
  File "./dmarctests.py", line 45, in <module>
    print("VERIFY: ", dkim.verify(signedmsg.decode('utf-8')))
  File "/usr/lib/python3/dist-packages/dkim/__init__.py", line 628, in verify
    d = DKIM(message,logger=logger,minkey=minkey)
  File "/usr/lib/python3/dist-packages/dkim/__init__.py", line 318, in __init__
    self.set_message(message)
  File "/usr/lib/python3/dist-packages/dkim/__init__.py", line 358, in set_message
    self.headers, self.body = rfc822_parse(message)
  File "/usr/lib/python3/dist-packages/dkim/__init__.py", line 207, in rfc822_parse
    lines = re.split(b"\r?\n", message)
  File "/usr/lib/python3.5/re.py", line 203, in split
    return _compile(pattern, flags).split(string, maxsplit)
TypeError: cannot use a bytes pattern on a string-like object