After upgrading Apereo CAS at our university to version 6.5.8 of cas-overlay, python-cas stopped working.

Verification of tickets CASClientWithSAMLV1 fails, server logs reveal that the CAS is unable to parse POST data. It turned out that the server does not like the <samlp:Request> tag split to multiple lines. When I join the lines, so that the whole tag is on a single line, it starts working.

Obviously, this is a bug in the server (or its dependencies) - multi-line tags are perfectly valid XML. However, I think that compressing the tag to a single line does not hurt and it works around the problem.