Fix futher Django Warnings.

mayan/apps/document_signatures/hooks.py

@@ -0,0 +1,43 @@
+from __future__ import unicode_literals
+
+import io
+import logging
+
+from django_gpg.exceptions import GPGDecryptionError
+from django_gpg.runtime import gpg
+
+logger = logging.getLogger(__name__)
+
+
+def document_pre_open_hook(descriptor, instance):
+    from .models import DocumentVersionSignature
+
+    if DocumentVersionSignature.objects.has_embedded_signature(document_version=instance):
+        # If it has an embedded signature, decrypt
+        try:
+            result = gpg.decrypt_file(descriptor, close_descriptor=False)
+            # gpg return a string, turn it into a file like object
+        except GPGDecryptionError:
+            # At least return the original raw content
+            descriptor.seek(0)
+            return descriptor
+        else:
+            descriptor.close()
+            return io.BytesIO(result.data)
+    else:
+        return descriptor
+
+
+def document_version_post_save_hook(instance):
+    logger.debug('instance: %s', instance)
+    from .models import DocumentVersionSignature
+
+    try:
+        document_signature = DocumentVersionSignature.objects.get(
+            document_version=instance
+        )
+    except DocumentVersionSignature.DoesNotExist:
+        document_signature = DocumentVersionSignature.objects.create(
+            document_version=instance
+        )
+        document_signature.check_for_embedded_signature()