Install Openslide in tests + typo

[Rylern]

No description provided.

[alanocallaghan]

Narrowed the test failure down to photometric="rgb" in tests/res/multi_resolution_uint8_3channels.py. Changing this fixes most of the tests, with one remaining failure:

tests/images/test_openslide_server.py:109: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
tmp/lib/python3.10/site-packages/numpy/_utils/__init__.py:85: in wrapper
    return fun(*args, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

args = (<built-in function eq>, array([[[0, 0, 0, ..., 0, 0, 0],
        [0, 0, 0, ..., 0, 0, 0],
        [0, 0, 0, ..., 0, 0...0, 251, 251],
        [  0,   0,   0, ..., 251, 252, 252],
        [  0,   0,   0, ..., 252, 253, 253]]], dtype=uint8))
kwds = {'err_msg': '', 'header': 'Arrays are not equal', 'strict': False, 'verbose': True}

    @wraps(func)
    def inner(*args, **kwds):
        with self._recreate_cm():
>           return func(*args, **kwds)
E           AssertionError: 
E           Arrays are not equal
E           
E           Mismatched elements: 387629 / 393216 (98.6%)
E           Max absolute difference among violations: 128
E           Max relative difference among violations: 1.
E            ACTUAL: array([[[0, 0, 0, ..., 0, 0, 0],
E                   [0, 0, 0, ..., 0, 0, 0],
E                   [0, 0, 0, ..., 0, 0, 0],...
E            DESIRED: array([[[  0,   0,   0, ..., 253, 254, 254],
E                   [  0,   0,   0, ..., 253, 254, 254],
E                   [  0,   0,   0, ..., 253, 254, 254],...

This is something Thibaut mentioned before, with some version of tiffslide/file reading all zeros. I guess this might also be an openslide vs tiffslide thing for why it works on some platforms and not others. Any ideas?