Raise meaningful error when Borg version found is too old. Fixes #283 (#287)

* Raise meaningful error when Borg version found is too old. Fixes #283

* Start with compatible Borg version to pass tests.

src/vorta/borg/_compatibility.py

@@ -3,6 +3,7 @@ from pkg_resources import parse_version
 MIN_BORG_FOR_FEATURE = {
     'BLAKE2': parse_version('1.1.4'),
     'ZSTD': parse_version('1.1.4'),
+    'JSON_LOG': parse_version('1.1.0')
     # add new version-checks here.
 }
 
@@ -14,7 +15,7 @@ class BorgCompatibility:
     to customize Borg commands by version in the future.
     """
 
-    version = '0.0'
+    version = '1.1.0'
     path = ''
 
     def set_version(self, version, path):

src/vorta/borg/borg_thread.py

@@ -13,7 +13,7 @@ from subprocess import Popen, PIPE
 
 from vorta.i18n import trans_late
 from vorta.models import EventLogModel, BackupProfileMixin
-from vorta.utils import keyring
+from vorta.utils import keyring, borg_compat
 from vorta.keyring.db import VortaDBKeyring
 
 mutex = QtCore.QMutex()
@@ -109,6 +109,10 @@ class BorgThread(QtCore.QThread, BackupProfileMixin):
             ret['message'] = trans_late('messages', 'Add a backup repository first.')
             return ret
 
+        if not borg_compat.check('JSON_LOG'):
+            ret['message'] = trans_late('messages', 'Your Borg version is too old. >=1.1.0 is required.')
+            return ret
+
         # Try to get password from chosen keyring backend.
         logger.debug("Using %s keyring to store passwords.", keyring.__class__.__name__)
         ret['password'] = keyring.get_password('vorta-repo', profile.repo.url)