Merge branch 'develop' into deserialized-data-dict

Conflicts:
	tasklib/task.py

diff --cc tasklib/task.py
index a739d25b46e2ebcc6137a7300fcb7bd1bc2618a9,b6c3d09168ec6897749ade2c2d4ce26ceebf2b33..8513b14f79cdebbd200bda6be3fc199a2946ef6a
--- 1/tasklib/task.py
--- 2/tasklib/task.py
+++ b/tasklib/task.py
@@@ -369,11 -372,13 +369,14 @@@ class Task(TaskResource)
  
          def add_field(field):
              # Add the output of format_field method to args list (defaults to
 -            # field:'value')
 -            format_default = lambda k: "{0}:{1}".format(k,
 -                                           "'{0}'".format(self._data[k])
 -                                           if self._data[k] is not None
 -                                           else '')
 +            # field:value)
 +            serialized_value = self._serialize(field, self._data[field]) or ''
-             format_default = lambda: "{0}:'{1}'".format(field, serialized_value)
++            format_default = lambda: "{0}:{1}".format(
++                field,
++                "'{0}'".format(serialized_value) if serialized_value else ''
++            )
              format_func = getattr(self, 'format_{0}'.format(field),
 -                                  lambda: format_default(field))
 +                                  format_default)
              args.append(format_func())
  
          # If we're modifying saved task, simply pass on all modified fields