Add some annoucement banner

Author: Gonchik Tsymzhitov

.travis.yml

@@ -7,7 +7,7 @@ python:
     - "3.6"
     - "3.7"
     - "3.8"
-    - "3.9"
+    - "3.9-dev"
 
 matrix:
   allow_failures:

atlassian/bitbucket.py

@@ -2181,3 +2181,43 @@ def get_associated_build_statuses(self, commit):
             url = '/rest/build-status/2.0/commits/{commitId}'.format(commitId=commit)
 
         return self.get(url)
+
+    def get_announcement_banner(self):
+        """
+        Gets the announcement banner, if one exists and is available to the user
+        :return:
+        """
+        if not self.cloud:
+            url = "rest/api/1.0/admin/banner"
+        else:
+            url = "rest/api/2.0/admin/banner"
+        return self.get(url)
+
+    def set_announcement_banner(self, body):
+        """
+        Sets the announcement banner with the provided JSON.
+        Only users authenticated as Admins may call this resource
+        :param body
+            {
+                "id": "https://docs.atlassian.com/jira/REST/schema/rest-announcement-banner#",
+                "title": "Rest Announcement Banner",
+                "type": "object"
+            }
+        :return:
+        """
+        if not self.cloud:
+            url = "rest/api/1.0/admin/banner"
+        else:
+            url = "rest/api/2.0/admin/banner"
+        return self.put(url, data=body)
+
+    def delete_announcement_banner(self):
+        """
+        Gets the announcement banner, if one exists and is available to the user
+        :return:
+        """
+        if not self.cloud:
+            url = "rest/api/1.0/admin/banner"
+        else:
+            url = "rest/api/2.0/admin/banner"
+        return self.delete(url)