Dump error if dotest itself fails and no tests were run.

[clayborg]

Looks fine.

lldb/trunk/test/dosep.py

if os.name != "nt":
                                             close_fds=True)
     else:
         process = subprocess.Popen(command, stdin=subprocess.PIPE,
                                             stdout=subprocess.PIPE,
                                             stderr=subprocess.PIPE)
     output = process.communicate()
     exit_status = process.returncode
     passes, failures = parse_test_results(output)
-    update_status(name, output if failures > 0 else None)
+    update_status(name, output if exit_status != 0 else None)
     return exit_status, passes, failures
 
 def process_dir(root, files, test_root, dotest_argv):
     """Examine a directory for tests, and invoke any found within it."""
     timed_out = []
     failed = []
     passed = []
     pass_sub_count = 0
for xtime in expected_timeout:
         else:
             result = None  # failed
 
         if result:
             test_name = os.path.splitext(xtime)[0]
             touch(os.path.join(session_dir, "{}-{}".format(result, test_name)))
 
     print
-    print "Ran %d test suites (%d failed) (%f%%)" % (num_test_files, len(failed), 100.0*len(failed)/num_test_files)
-    print "Ran %d test cases (%d failed) (%f%%)" % (num_tests, all_fails, 100.0*all_fails/num_tests)
+    print "Ran %d test suites (%d failed) (%f%%)" % (num_test_files, len(failed),
+            (100.0 * len(failed) / num_test_files) if num_test_files > 0 else float('NaN'))
+    print "Ran %d test cases (%d failed) (%f%%)" % (num_tests, all_fails,
+            (100.0 * all_fails / num_tests) if num_tests > 0 else float('NaN'))
     if len(failed) > 0:
         failed.sort()
         print "Failing Tests (%d)" % len(failed)
         for f in failed:
             print "%s: LLDB (suite) :: %s (%s)" % (
                 "TIMEOUT" if f in timed_out else "FAIL", f, system_info
             )
         sys.exit(1)
     sys.exit(0)
 
 if __name__ == '__main__':
     main()