Three slightly different points here:

1. Decoding trailing whitespace: My understanding is quoted-printable encoding aims to be tolerant of whitespace being added to and removed from the end of encoded lines. So I assume the “binascii” module is wrong to leave trailing whitespace in the decoded output, and the native “quopri” implementation is correct to ignore it.

2. CRLF handling: See Issue 20121. It seems CRLF newlines should be valid, and I have added a patch to that issue to make the native Python implementation handle CRLF newlines.

3. Whitespace encoding: The quopri-codec actually sets quotetabs=True. Here is a patch to document and test that, as well as correct the functions used by other codecs.