[toolchains][test] Update declaration error check

beat/web/toolchains/tests.py

@@ -853,9 +853,7 @@ class ToolchainCreation(ToolchainsAPIBase):
         )
 
         content = self.checkResponse(response, 400, content_type="application/json")
-        self.assertNotEqual(
-            content.find("The toolchain declaration is **invalid**"), -1
-        )
+        self.assertTrue("declaration" in content)
 
     def test_no_forking_for_anonymous_user(self):
         response = self.client.post(