Test on multiple Pint versions

[mattwthompson]

Description

I'd like to make sure tests pass with both Pint 0.21 and 0.22, which was recently released.

Todos

Notable points that this PR has either accomplished or will accomplish.

• TODO 1

Questions

• Question1

Status

• Ready to go

[codecov-commenter]

Codecov Report

Merging #67 (ed31fc3) into main (b5af837) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

[mattwthompson]

Well, that's confusing.

>>> from openff.units import unit
>>> from openff.units.openmm import to_openmm
>>> x = unit.Quantity(1, "nanometer")
>>> to_openmm(x)
Quantity(value=1, unit=nanometer)
>>> x.to_openmm()
Traceback (most recent call last):
  File "/Users/mattthompson/mambaforge/envs/openff-units-test/lib/python3.10/site-packages/pint/facets/numpy/quantity.py", line 229, in __getattr__
    return getattr(self._magnitude, item)
AttributeError: 'int' object has no attribute 'to_openmm'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/mattthompson/mambaforge/envs/openff-units-test/lib/python3.10/site-packages/pint/facets/numpy/quantity.py", line 231, in __getattr__
    raise AttributeError(
AttributeError: Neither Quantity object nor its magnitude (1) has attribute 'to_openmm'

[mattwthompson]

I don't know why this way of monkey-patch works and the old way didn't. I'm scared to learn why.

https://github.com/hgrecco/pint/pull/1633/files