Unflake hypothesis tests

Restrict hypothesis strategies generating interaction types and molecule names from using characters in the unicode classes Z (separators) and C (control characters).

vermouth/tests/molecule_strategies.py

@@ -148,7 +148,7 @@ def interaction_collection(draw, graph,
     ninteraction_types = draw(st.integers(min_value=0, max_value=2))
     for _ in range(ninteraction_types):
         ninteractions = draw(st.integers(min_value=0, max_value=2))
-        type_name = draw(st.text())
+        type_name = draw(st.text(st.characters(blacklist_categories=('C', 'Z')), min_size=1))
         if type_name not in result:
             result[type_name] = []
         for _ in range(ninteractions):

vermouth/tests/test_molecule.py

@@ -1229,7 +1229,13 @@ def test_interaction_sort(interactions, expected):
     assert vermouth.molecule.Molecule.sort_interactions(interactions) == expected
 
 
-@hypothesis.given(moltype=st.one_of(st.none(), st.text()), mol=random_molecule())
+@hypothesis.given(
+    moltype=st.one_of(
+        st.none(),
+        st.text(st.characters(blacklist_categories=('C', 'Z')), min_size=1)
+    ),
+    mol=random_molecule()
+)
 def test_str_method(mol, moltype):
     """
     Test Molecule.__str__