I have been working with the Blog module in my localhost dev site and decided that I needed to add a category menu with the blog category widget. I installed the Widgets module but the Widgets tab didn't appear in the CMS for my blog page.
From the instructions at https://github.com/silverstripe/silverstripe-widgets/blob/master/docs/en/getting-started.md, I realised that I needed to enable the WidgetPageExtension by adding the supplied lines to the config.yml file. This I did, ran a /dev/build and, since then, I've been getting a 500 error. I've removed the lines from config.yml but, since I can't re-run a /dev/build, I can't get back to my site. I've cleared the browser cache but that does nothing. Other localhost sites are running fine.
I am (or at least was!) running SS 3.4.1 via WAMP.
Please help 'cos I'm completely stuck! Thanks.