io.py incompatible with PyYAML-6.0

[nieder]

When building meza, this test failure happens:

Doctest: meza.io.read_yaml ... FAIL

======================================================================
FAIL: Doctest: meza.io.read_yaml
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/sw/lib/python3.9/doctest.py", line 2205, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for meza.io.read_yaml
  File "/sw/build.build/meza-py39-0.46.0-1/meza-0.46.0/meza/io.py", line 1256, in read_yaml

----------------------------------------------------------------------
File "/sw/build.build/meza-py39-0.46.0-1/meza-0.46.0/meza/io.py", line 1279, in meza.io.read_yaml
Failed example:
    next(records) == {
        'text': 'Chicago Reader',
        'float': 1.0,
        'datetime': dt(1971, 1, 1, 4, 14),
        'boolean': True,
        'time': '04:14:00',
        'date': date(1971, 1, 1),
        'integer': 40}
Exception raised:
    Traceback (most recent call last):
      File "/sw/lib/python3.9/doctest.py", line 1334, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest meza.io.read_yaml[3]>", line 1, in <module>
        next(records) == {
      File "/sw/build.build/meza-py39-0.46.0-1/meza-0.46.0/meza/io.py", line 551, in read_any
        for line in _read_any(f, reader, args, **kwargs):
      File "/sw/build.build/meza-py39-0.46.0-1/meza-0.46.0/meza/io.py", line 470, in _read_any
        for num, line in enumerate(reader(f, *args, **kwargs)):
    TypeError: load() missing 1 required positional argument: 'Loader'

In

meza/meza/io.py

Line 1289 in 370c292

return read_any(filepath, yaml.load, mode, **kwargs)

, changing yaml.load to yaml.safe_load takes care of the problem (not sure what version yaml.safe_load was introduced).
See yaml/pyyaml#576