Allow form.widgets.RenderTemplateWidget to use the theme object

Author: cjmayo

flask_admin/base.py

@@ -548,6 +548,8 @@ def __init__(self, app=None, name=None,
         # Register with application
         if app is not None:
             self._init_extension()
+            # Make theme available via current_app
+            app.config['theme'] = self.theme
 
     def _validate_admin_host_and_subdomain(self):
         if self.subdomain is not None and self.host is not None:

flask_admin/form/widgets.py

@@ -90,6 +90,7 @@ def __call__(self, field, **kwargs):
             '_gettext': gettext,
             '_ngettext': ngettext,
             'h': h,
+            'theme': current_app.config['theme'],
         })
 
         template = current_app.jinja_env.get_template(self.template)