make end-to-end test failure more verbose

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

test/end-to-end-tests/src/usecases/signup.js

@@ -61,7 +61,7 @@ module.exports = async function signup(session, username, password, homeserver)
     await session.query(".mx_Field_valid #mx_RegistrationForm_password");
     //check no errors
     const errorText = await session.tryGetInnertext('.mx_Login_error');
-    assert.strictEqual(!!errorText, false);
+    assert.strictEqual(errorText, null);
     //submit form
     //await page.screenshot({path: "beforesubmit.png", fullPage: true});
     await registerButton.click();