Add new Buefy-specific upgrade template

since that was broken..

tailbone/views/master.py

@@ -24,6 +24,7 @@
 Model Master View
 """
 
+import io
 import os
 import csv
 import datetime
@@ -33,7 +34,6 @@ import tempfile
 import logging
 
 import json
-import six
 import sqlalchemy as sa
 from sqlalchemy import orm
 import sqlalchemy_continuum as continuum
@@ -115,6 +115,7 @@ class MasterView(View):
     executable = False
     execute_progress_template = None
     execute_progress_initial_msg = None
+    execute_can_cancel = True
     supports_prev_next = False
     supports_import_batch_from_file = False
     has_input_file_templates = False
@@ -1839,6 +1840,7 @@ class MasterView(View):
         return self.render_progress(progress, {
             'instance': obj,
             'initial_msg': self.execute_progress_initial_msg,
+            'can_cancel': self.execute_can_cancel,
             'cancel_url': self.get_action_url('view', obj),
             'cancel_msg': "{} execution was canceled".format(model_title),
         }, template=self.execute_progress_template)
@@ -3785,7 +3787,7 @@ class MasterView(View):
         """
         obj = self.get_instance()
         fields = self.get_row_csv_fields()
-        data = six.StringIO()
+        data = io.StringIO()
         writer = UnicodeDictWriter(data, fields)
         writer.writeheader()
         for row in self.get_effective_row_data(sort=True):

tailbone/views/upgrades.py

@@ -60,6 +60,7 @@ class UpgradeView(MasterView):
     executable = True
     execute_progress_template = '/upgrade.mako'
     execute_progress_initial_msg = "Upgrading"
+    execute_can_cancel = False
 
     labels = {
         'executed_by': "Executed by",