ENH: improve SG key formatting in GetSpaceGroup

Try to match key formats in `short_name` and `pdb_name`.

Author: pavoljuhas

src/diffpy/structure/spacegroups.py

@@ -43,17 +43,14 @@ def GetSpaceGroup(sgid):
     emsg = "Unknown space group identifier %r" % sgid
     if not isinstance(sgid, six.string_types):
         raise ValueError(emsg)
-    # short name case adjusted
-    sgkey = sgid.strip()
+    sgbare = sgid.strip()
+    # short_name case adjusted
+    sgkey = sgbare.replace(' ', '')
     sgkey = sgkey[:1].upper() + sgkey[1:].lower()
     if sgkey in _sg_lookup_table:
         return _sg_lookup_table[sgkey]
-    # long name all upper case
-    sgkey = sgid.strip().upper()
-    if sgkey in _sg_lookup_table:
-        return _sg_lookup_table[sgkey]
-    # try to remove any blanks
-    sgkey = sgid.replace(' ', '')
+    # pdb_name case adjusted
+    sgkey = sgbare[:1].upper() + sgbare[1:].lower()
     if sgkey in _sg_lookup_table:
         return _sg_lookup_table[sgkey]
     # nothing worked, sgid is unknown identifier