ADD support for creating subtasks in JIRA

* Add support for creating Sub Task

Fixes #26

Signed-off-by: Abhijeet Kasurde <akasurde@redhat.com>

* Fix parent field

According to JIRA API 'parent' field must be object with 'key' or 'id'.

* Added subtasks docs

* Fix _prepare_ticket_fields()

read-the-docs/source/JIRA.rst

@@ -55,6 +55,10 @@ particular JIRA instance during ticket creation:
     parent='KEY-XX'
     customfield_XXXXX='Custom field text'
 
+While creating a Sub task, parent ticket id is required, otherwise create()
+method fails with KeyError - "Parent field is required while creating a Sub
+Task"
+
 edit()
 ------
 
@@ -256,3 +260,25 @@ Update existing JIRA tickets
     # Close Requests session.
     ticket.close_requests_session()
 
+Create a Sub-Task inside existing JIRA ticket
+---------------------------------------------
+
+.. code:: python
+
+    from ticketutil.jira import JiraTicket
+
+    # Create a ticket object and pass the url and project key in as strings.
+    t = JiraTicket(<jira_url>,
+                   <project_key>,
+                   auth=('username', 'password'))
+
+    # Create a ticket and perform some common ticketing operations.
+    t.create(summary='Sub Task summary',
+             description='Sub Task description',
+             assignee='username',
+             type='Sub-task',
+             parent='existing_ticket_id')
+    t.change_status('In Progress')
+
+    # Close Requests session.
+    t.close_requests_session()

ticketutil/jira.py

@@ -459,13 +459,20 @@ def _prepare_ticket_fields(fields):
         Makes sure each key value pair in the fields dictionary is in the correct form.
         :param fields: Ticket fields.
         :return: fields: Ticket fields in the correct form for the ticketing tool.
+        :raises: KeyError: While creating Sub Task, if parent is not provided.
         """
+        if fields['type'] == 'Sub-task' and 'parent' not in fields:
+            raise KeyError("Parent field is required while creating a Sub Task")
+
         for key, value in fields.items():
-            if key in ['priority', 'assignee', 'reporter', 'parent']:
+            if key in ['priority', 'assignee', 'reporter']:
                 fields[key] = {'name': value}
+            if key in ['parent']:
+                fields[key] = {'key': value}
             if key == 'type':
                 fields['issuetype'] = {'name': value}
                 fields.pop('type')
+
         return fields