Django GPG: 3rd party app compatibility update

Update the django_gpg app to work with the latest version of the
python-gnupg package (0.4.3).

The python-gnupg now returns a more clear error message to
differentiate between a bad passphrase and a missing passphrase.
This improments allows the django_gpg to simplify its error
message parsing and remove the literals:
"ERROR_MSG_NEED_PASSPHRASE" and "ERROR_MSG_GOOD_PASSPHRASE".

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

HISTORY.rst

@@ -151,6 +151,9 @@
   ``DOCUMENT_SIGNATURES_STORAGE_BACKEND_ARGUMENTS``. This
   change differentiates them from the setting from the 
   django_gpg app.
+- Updated the django_gpg app to work with the latest
+  version of the python-gnupg package (0.4.3).
+
 
 3.1.9 (2018-11-01)
 ==================

mayan/apps/django_gpg/literals.py

@@ -5,6 +5,9 @@ from django.utils.translation import ugettext_lazy as _
 DEFAULT_GPG_PATH = '/usr/bin/gpg1'
 DEFAULT_SETTING_GPG_BACKEND = 'mayan.apps.django_gpg.classes.PythonGNUPGBackend'
 
+ERROR_MSG_BAD_PASSPHRASE = 'BAD_PASSPHRASE'
+ERROR_MSG_MISSING_PASSPHRASE = 'MISSING_PASSPHRASE'
+
 KEY_TYPES = {
     'pub': _('Public'),
     'sec': _('Secret'),
@@ -34,13 +37,14 @@ KEY_SECONDARY_CLASSES = (
 
 KEYSERVER_DEFAULT_PORT = 11371
 
+OUTPUT_MESSAGE_CONTAINS_PRIVATE_KEY = 'Contains private key'
+
 SIGNATURE_STATE_BAD = 'signature bad'
 SIGNATURE_STATE_NONE = None
 SIGNATURE_STATE_ERROR = 'signature error'
 SIGNATURE_STATE_NO_PUBLIC_KEY = 'no public key'
 SIGNATURE_STATE_GOOD = 'signature good'
 SIGNATURE_STATE_VALID = 'signature valid'
-
 SIGNATURE_STATES = {
     SIGNATURE_STATE_BAD: {
         'text': _('Bad signature.'),
@@ -64,8 +68,3 @@ SIGNATURE_STATES = {
         'text': _('Document is signed with a valid signature.'),
     },
 }
-
-ERROR_MSG_NEED_PASSPHRASE = 'NEED_PASSPHRASE'
-ERROR_MSG_BAD_PASSPHRASE = 'BAD_PASSPHRASE'
-ERROR_MSG_GOOD_PASSPHRASE = 'GOOD_PASSPHRASE'
-OUTPUT_MESSAGE_CONTAINS_PRIVATE_KEY = 'Contains private key'

mayan/apps/django_gpg/models.py

@@ -11,9 +11,8 @@ from django.utils.translation import ugettext_lazy as _
 
 from .exceptions import NeedPassphrase, PassphraseError
 from .literals import (
-    ERROR_MSG_NEED_PASSPHRASE, ERROR_MSG_BAD_PASSPHRASE,
-    ERROR_MSG_GOOD_PASSPHRASE, KEY_TYPE_CHOICES, KEY_TYPE_SECRET,
-    OUTPUT_MESSAGE_CONTAINS_PRIVATE_KEY
+    ERROR_MSG_BAD_PASSPHRASE, ERROR_MSG_MISSING_PASSPHRASE,
+    KEY_TYPE_CHOICES, KEY_TYPE_SECRET, OUTPUT_MESSAGE_CONTAINS_PRIVATE_KEY
 )
 from .managers import KeyManager
 from .runtime import gpg_backend
@@ -124,10 +123,10 @@ class Key(models.Model):
 
         logger.debug('file_sign_results.stderr: %s', file_sign_results.stderr)
 
-        if ERROR_MSG_NEED_PASSPHRASE in file_sign_results.stderr:
-            if ERROR_MSG_BAD_PASSPHRASE in file_sign_results.stderr:
-                raise PassphraseError
-            elif ERROR_MSG_GOOD_PASSPHRASE not in file_sign_results.stderr:
-                raise NeedPassphrase
+        if ERROR_MSG_MISSING_PASSPHRASE in file_sign_results.stderr:
+            raise NeedPassphrase
+
+        if ERROR_MSG_BAD_PASSPHRASE in file_sign_results.stderr:
+            raise PassphraseError
 
         return file_sign_results

mayan/apps/django_gpg/settings.py

@@ -1,8 +1,5 @@
 from __future__ import unicode_literals
 
-import os
-
-from django.conf import settings
 from django.utils.translation import ugettext_lazy as _
 
 from mayan.apps.smart_settings import Namespace