Remove last two remaining from external imports

lib/spack/spack/cmd/repo.py

@@ -26,7 +26,7 @@
 import re
 import shutil
 
-from external import argparse
+import argparse
 import llnl.util.tty as tty
 from llnl.util.filesystem import join_path, mkdirp
 

lib/spack/spack/repository.py

@@ -30,7 +30,7 @@
 import re
 import traceback
 from bisect import bisect_left
-from external import yaml
+import yaml
 
 import llnl.util.tty as tty
 from llnl.util.filesystem import *