make dump style yaml test dependent on it being available

unittest/python/python-formats.py

@@ -116,18 +116,18 @@ class AvgChunkFiles(unittest.TestCase):
 
 
 from lammps import lammps
-has_full = False
+has_dump_yaml = False
 try:
     machine=None
     if 'LAMMPS_MACHINE_NAME' in os.environ:
         machine=os.environ['LAMMPS_MACHINE_NAME']
     lmp=lammps(name=machine)
-    has_full = lmp.has_style("atom","full")
+    has_dump_yaml = lmp.has_style("atom","full") && lmp.has_style("dump", "yaml")
     lmp.close()
 except:
     pass
 
-@unittest.skipIf(not has_full, "atom_style full is not available")
+@unittest.skipIf(not has_dump_yaml, "Either atom_style full or dump_style yaml are not available")
 class PythonDump(unittest.TestCase):
     def setUp(self):
         machine = None