PDBxFile only closes input file if it opens it.

wrappers/python/simtk/openmm/app/pdbxfile.py

@@ -70,12 +70,15 @@ class PDBxFile(object):
         # Load the file.
 
         inputFile = file
+        ownHandle = False
         if isinstance(file, str):
             inputFile = open(file)
+            ownHandle = True
         reader = PdbxReader(inputFile)
         data = []
         reader.read(data)
-        inputFile.close()
+        if ownHandle:
+            inputFile.close()
         block = data[0]
 
         # Build the topology.