This error occurs on ezplatform-demo (and ezplatform-ee-demo) with the demo content. This does not occur on the clean install.

Steps to reproduce:

• Install ezplatform-demo 2.0

  composer create-project ezsystems/ezplatform-demo:2.0
  cd ezplatform-demo/
  bin/console ezplatform:install platform-demo
  

• go to /admin

Result:
error 500:

An exception has been thrown during the rendering of a template ("User does not have access to 'view' 'section'"). [in vendor/ezsystems/ezplatform-admin-ui/src/bundle/Resources/views/content/locationview.html.twig:49]

Expected result:
be redirected to the login page

More technical information

The difference between the clean install and the demo install is the user/login policy.
On the clean install:
user / login / SiteAccess: site
On the demo install:
user / login / no limitation

Adding a SiteAccess (EXCEPT admin) to user/login policy is enough to redirect the user...

Scenarios

Here how the login policy should work (it was like that on legacy):

No limitation

Given the anonymous role has user/login with no limitation
And I am not logged in
When I access to the login page on every available siteaccess
Then I see the login form

SiteAccess limitation

Given the anonymous role has user/login with SiteAccess: *fr* 
And I am not logged in
When I access to the login page on *fr* siteaccess
Then I see the login form

Given the anonymous role has user/login with SiteAccess: *fr* 
And I am not logged in
When I access to the login page on *admin* siteaccess
Then I get the error 403 page: You don’t have permission for this page.