Add exit code when running all tests with iptest.

IPython/testing/iptest.py

@@ -425,6 +425,8 b' def run_iptestall():'
             print 'You may wish to rerun this one individually, with:'
             print ' '.join(failed_runner.call_args)
             print
+            # Ensure that our exit code indicates failure
+            sys.exit(1)
 
 
 def main():