suppress stderr output when checking gdb (closes #27969)

Author: benjaminp

Lib/test/test_gdb.py

@@ -25,6 +25,7 @@ def get_gdb_version():
     try:
         proc = subprocess.Popen(["gdb", "-nx", "--version"],
                                 stdout=subprocess.PIPE,
+                                stderr=subprocess.PIPE,
                                 universal_newlines=True)
         with proc:
             version = proc.communicate()[0]