Error after fresh install

Oh, that sounds like a specific bug of your php version.

I tried to add a test example to http://3v4l.org/JcRtA but it certainly doesn't fail ... also the testbot runs on 5.4, so it should fail immediately.

I've seen this one before, seems to be a PHP version where aliases traits aren't working...

Searching for "traitSleep" pointed me to #2347661: PHP Unit tests are broken on Windows. My guess is that you're using windows?

I think we can close this as duplicate, possibly raising the other one to major, but I think not critical?

Well, if it were currently impossible to install D8 on Windows using a PHP version we support, then that would be critical. Edit: The options would either be to fix it, to recommend a workaround, or to not support that version on Windows.

@Andrzej7, can you provide more information on your specific environment and the steps to reproduce the issue? I.e. do you get the message while running the installer? Does it appear just once and go away, or is the site totally unusable? Does installation fail entirely? (Be sure to start clean.)

At least for this error message we don't have to fight with windows.

@Andrzej7
Which distribution do you use exactly?

Ok, this is weird.

php 5.4.36-0+tld0 doesn't look like windows at all, that looks like a typical linux distribution suffix. Google finds very few hits, but someone was nice enough to leave the symfony debugger on and was using that version. The IP points to tld.pl (look, the suffix matches!), but there's nothing to see :p

Accessing the IP directly in turn points to https://www.kei.pl/, a polnish web hoster. Looks like they broke their PHP :p

We can't fight against broken PHP

Well, let's wait to hear back. Presumably this will end up closed as a wontfix since we can't really do anything about rare PHP bugs in specific distros.

d8 dev environment tag to add to the collection of problems people have getting a local to work.

Waiting for provider feedback then ...

I think this is a duplicate of #2421419: CategorizingPluginManagerTrait not compatible with CategorizingPluginManagerInterface

@alexpott: Same category of problems (bugs with specific php versions), but why do you think it is a duplicate?

So far we don't know what the problem is, it's not just that PHP version. Unlike the other issue, which can easily be reproduced on 3v4l.org, this one works fine on that version.

@Berdir I guess you right - it certainly looks a bug of a similar nature.

Boldly bumping this down, because looks to be environment specific.
Feel free to disagree.

@Andrzej7 Drupal 8's minimum PHP version is 5.5 - in the issue summary it's saying php5.4 - I guess beta12 was before the version change.

@Andrzej7 see #2508231: Raise minimum required version of PHP to 5.5.9

Now you're running into #2529188: Provide better error handling for MySQL client and server utf8mb4 incompatibility. You certainly have a fun hoster ;)