fixed typo

seems that you have to play with casp structures to produce such errors...

modules/bindings/pymod/dssp.py

@@ -111,7 +111,7 @@ def AssignDSSP(ent, pdb_path="", extract_burial_status=False, tmp_dir=None,
   # are handled in the parser LoadDSSP)
   temp_dssp_path=_ExecuteDSSP(pdb_path, dssp_bin)
   if not os.path.exists(temp_dssp_path):
-    raise RuntimeEror('DSSP output file does not exist.')
+    raise RuntimeError('DSSP output file does not exist.')
   # assign DSSP to entity
   try:
     LoadDSSP(temp_dssp_path, ent, extract_burial_status,