community/py3-websocket-client: correct license and modernize
A big part of the 1.2.x upgrade was relicensing from partial (and incorrect) LGPL to Apache-2.0. Let's reflect that in our packaging
Also modernize while we're at it:
- add missing indents
- move to pytest for check function
- remove use of _pkgname
- stop renaming the source tarball and instead download correct name directly from upstream