Currently, running `yarn test-pwa-score` right after deploying to staging fails
with the error:
```
{ Error: Unable to load the page: timeout reached ... code: 'PAGE_LOAD_ERROR' }
```
As a temporary fix, this commit prevents the build from failing because of PWA
score errors (until we identify the cause and fix it).
Previously, when trying to upload the build artifacts for a PR/SHA that was
already successfully deployed (e.g. when re-running a Travis job), the preview
server would return a 403 and the build would fail.
Since we have other mechanisms to verify that the PR author is trusted and the
artifacts do indeed come from the specified PR and since the new artifacts
should be the same with the already deployed ones (same SHA), there is no reason
to fail the build. The preview server will reject the request with a special
HTTP status code (409 - Conflict), which the `deploy-preview` script will
recognize and exit with 0.
This reverts commit d0bc83ca275964fa1de6684c3cdc6714de386efd.
Protractor-based prerendering is flakey on Travis and takes several minutes to
complete, slowing down the build. Prerendering has a lower impact now that we
use a ServiceWorker. We will revisit in the future (probably using a
`PlatformServer`-based approach).
PR Close#15346
Gaining access to another PR's JWT, would allow faking that PR's author wrt to
GitHub team membership verification for as long as the JWT is valid (currently
90 mins).
