Here is a patch that clarifies in the documentation and test suite how newlines work in the “quopri” and “binascii” modules. It also fixes the native Python implementation to support CRLFs.

* \n is used by default (e.g. for soft line breaks if the input has no hard line breaks)
* CRLF is used instead if found in input (even in non-text mode!)
* Typo errors in documentation
* quopri uses istext=True
* header flag does not affect newline encoding; only istext affects it

One corner case concerns me slightly: binascii.b2a_qp(istext=False) will use \n for soft line breaks by default, but will suddenly switch to CRLF if the input data happens to contain a CRLF sequence. This is despite the CRLFs from the data being encoded and therefore not appearing in the output themselves.