skip failing TestPackmolSet.test_random_seed due to openbabel not ins…

…talled

pymatgen/io/tests/test_packmol.py:188:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

args = (<pymatgen.analysis.molecule_matcher.MoleculeMatcher object at 0x2aecc7bd0>,)
kwargs = {}

    @functools.wraps(_callable)
    def decorated(*args, **kwargs):
        if not self.condition:
>           raise RuntimeError(self.message)
E           RuntimeError: BabelMolAdaptor requires openbabel to be installed with Python bindings. Please get it at http://openbabel.org (version >=3.0.0).

pymatgen/io/tests/test_packmol.py

@@ -185,6 +185,7 @@ def test_random_seed(self):
         Confirm that seed = -1 generates random structures
         while seed = 1 is deterministic
         """
+        pytest.importorskip("openbabel")
         mm = MoleculeMatcher()
 
         # deterministic output