Fixed following schema diff issues:

1) Avoid template databases from the Database drop-down list.
 2) Exclude system schemas while comparing two databases.
 3) Escape group name for XSS.

web/pgadmin/browser/server_groups/servers/databases/__init__.py

@@ -251,9 +251,16 @@ class DatabaseView(PGChildNodeView):
                 'datlastsysoid']
         return last_system_oid
 
-    def get_nodes(self, gid, sid, show_system_templates=False):
+    def get_nodes(self, gid, sid, is_schema_diff=False):
         res = []
         last_system_oid = self.retrieve_last_system_oid()
+
+        # if is_schema_diff then no need to show system templates.
+        if is_schema_diff and self.manager.db_info is not None and \
+                self.manager.did in self.manager.db_info:
+            last_system_oid = \
+                self.manager.db_info[self.manager.did]['datlastsysoid']
+
         server_node_res = self.manager
 
         db_disp_res = None
@@ -303,8 +310,8 @@ class DatabaseView(PGChildNodeView):
         return res
 
     @check_precondition(action="nodes")
-    def nodes(self, gid, sid):
-        res = self.get_nodes(gid, sid)
+    def nodes(self, gid, sid, is_schema_diff=False):
+        res = self.get_nodes(gid, sid, is_schema_diff)
 
         return make_json_response(
             data=res,

web/pgadmin/browser/server_groups/servers/databases/schemas/__init__.py

@@ -413,7 +413,7 @@ class SchemaView(PGChildNodeView):
         )
 
     @check_precondition
-    def nodes(self, gid, sid, did, scid=None):
+    def nodes(self, gid, sid, did, scid=None, is_schema_diff=False):
         """
         This function will create all the child nodes within the collection
         Here it will create all the schema node.
@@ -422,6 +422,8 @@ class SchemaView(PGChildNodeView):
             gid: Server Group ID
             sid: Server ID
             did: Database ID
+            scid: Schema ID
+            is_schema_diff: True if called by schema diff tool
 
         Returns:
             JSON of available schema child nodes
@@ -437,9 +439,13 @@ class SchemaView(PGChildNodeView):
                     ["'%s'"] * len(schema_restrictions.split(',')))
                 param = schema_res % (tuple(schema_restrictions.split(',')))
 
+        show_system_objects = self.blueprint.show_system_objects
+        if is_schema_diff:
+            show_system_objects = False
+
         SQL = render_template(
             "/".join([self.template_path, self._SQL_PREFIX + self._NODES_SQL]),
-            show_sysobj=self.blueprint.show_system_objects,
+            show_sysobj=show_system_objects,
             _=gettext,
             scid=scid,
             schema_restrictions=param