Fix Flaky test_execute_on_shift_enter (#1097)

* Wait for text to render in DOM before 'assert', to fix timing issue.

pyscriptjs/tests/integration/test_py_repl.py

@@ -1,4 +1,4 @@
-from .support import PyScriptTest
+from .support import PyScriptTest, wait_for_render
 
 
 class TestPyRepl(PyScriptTest):
@@ -65,6 +65,7 @@ class TestPyRepl(PyScriptTest):
         )
         self.page.wait_for_selector("#runButton")
         self.page.keyboard.press("Shift+Enter")
+        wait_for_render(self.page, "*", "hello world")
 
         assert self.console.log.lines[0] == self.PY_COMPLETE
         assert self.console.log.lines[-1] == "hello world"