The methode JWEnc.is_jwe does not work correctly when Python was called with the "-O" or "-OO" option

[wmeyer]

The method mentioned in the title uses the "assert" statement to check the headers of a token.

Unfortunately, assert statements are completely removed when starting Python with "-O" (or "-OO").
See here https://docs.python.org/3/using/cmdline.html#miscellaneous-options

As a result, the OIDC connection cannot be established.

Recommended fix: Use "if" statements in such cases.

I found two more issues like this relevant to my usecase:

• method JWS._is_compact_jws
• Operator __eq__ in class jwk.Key

Note: #99 fixes the first of these issues, but not the other ones.