Actually validate hooks

letsencrypt/cli.py

@@ -18,6 +18,7 @@ import letsencrypt
 from letsencrypt import constants
 from letsencrypt import crypto_util
 from letsencrypt import errors
+from letsencrypt import hooks
 from letsencrypt import interfaces
 from letsencrypt import le_util
 
@@ -306,6 +307,8 @@ class HelpfulArgumentParser(object):
         if self.detect_defaults:  # plumbing
             parsed_args.store_false_vars = self.store_false_vars
 
+        hooks.validate_hooks(parsed_args)
+
         return parsed_args
 
     def handle_csr(self, parsed_args):

letsencrypt/hooks.py

@@ -27,7 +27,7 @@ def _validate_hook(shell_cmd):
     :raises .errors.HookCommandNotFound: if the command is not found
     """
     cmd = shell_cmd.partition(" ")[0]
-    if not _prog(cmd):
+    if shell_cmd and not _prog(cmd):
         path = os.environ["PATH"]
         msg = "Unable to find command {0} in the PATH.\n(PATH is {1})".format(
             cmd, path)