pyyaml 6.0 breaks xicam

[rohandhall]

I get the error in gui/cammart/packagemanager.py, line 159:

self._store = yaml.load(f.read()) or {}
TypeError: load() missing 1 required positional argument: 'Loader'

pip install pyyaml==5.4.1 fixes the issue, but the new version of pyyaml has changed the load() function