core: Fix unicode bug on ZODB History view.

Some objects, in our case BTrees.Length.Length in a ZODB connection
have a __str__ method that returns unicode on python2:

u'<BTrees.Length.Length object at 0x7f850932e0d0 oid 0x1e334 in <Connection at 7f854bc0f190>>'

They cause an unicode error in the history view when they are
concatenated together with other str (encoded as UTF-8) properties,
this can be observed when using history view with a "folderish"
document (but not with a File as in test_ZODBHistoryBinaryData).

To prevent this issue, we use the fact that ''.format unlike '' %
seem to apply a str() on arguments and use it instead.
Co-authored-by: Yusei Tahara <yusei@nexedi.com>

bt5/erp5_core_test/TestTemplateItem/portal_components/test.erp5.testZODBHistory.py

@@ -134,6 +134,17 @@ class TestZODBHistory(ERP5TypeTestCase):
     from zExceptions import Unauthorized
     self.assertRaises(Unauthorized, document.Base_viewZODBHistory)
 
+  def test_ZODBHistoryNonAsciiProperty(self):
+    self.loginByUserName('tatuya')
+    document = self.addOrganisation(self.id())
+    document.edit(title='ネクセディ', default_address_city='千代田区')
+    self.commit()
+    _, change, = document.Base_getZODBHistoryList()
+    self.assertIn('title:ネクセディ', change.getProperty('changes'))
+
+    # no encoding error
+    document.Base_viewZODBHistory()
+
   def test_ZODBHistoryBinaryData(self):
     """
      Make sure ZODB History view works with binary content

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/Base_getZODBHistoryList.py

@@ -16,7 +16,7 @@ def beautifyChange(change_dict):
         six.text_type(property_value, 'utf-8')
       except UnicodeDecodeError:
         property_value = '(binary)'
-    change_list.append('%s:%r' % (property_name, property_value))
+    change_list.append('{}:{}'.format(property_name, property_value))
   return change_list
 
 try: