Do not fail encrypt() if the public key is already in our keyring

pgp_mime_lib/__init__.py

@@ -262,7 +262,9 @@ def _import_one_key(gpg, public_key):
 
     fp = None
     for res in import_result.results:
-        if "Entirely new key" not in res["text"]:
+        # "Not actually changed" in those cases, such as testing,
+        # where the public key is already in our keyring.
+        if ('Entirely new key' not in res['text']) and ('Not actually changed' not in res['text']):
             raise Error('no valid keys found in input: %r' % res['text'])
         if not res['fingerprint']:
             continue