Issue #8600: fix test_gdb failures when gdb issues some spurious warnings.

Lib/test/test_gdb.py

@@ -119,6 +119,11 @@ class DebuggerTests(unittest.TestCase):
 
         # Ignore some noise on stderr due to the pending breakpoint:
         err = err.replace('Function "%s" not defined.\n' % breakpoint, '')
+        # Ignore some other noise on stderr (http://bugs.python.org/issue8600)
+        err = err.replace("warning: Unable to find libthread_db matching"
+                          " inferior's thread library, thread debugging will"
+                          " not be available.\n",
+                          '')
 
         # Ensure no unexpected error messages:
         self.assertEquals(err, '')