TST: support test selection in the debug script.

The debug.py utility takes optional regular-expression pattern
to select specific test cases to be run.

Author: pavoljuhas

src/diffpy/Structure/tests/debug.py

@@ -24,8 +24,10 @@
 
 
 if __name__ == '__main__':
+    import sys
     from diffpy.Structure.tests import testsuite
-    suite = testsuite()
+    pattern = sys.argv[1] if len(sys.argv) > 1 else ''
+    suite = testsuite(pattern)
     suite.debug()