Symfony 4: You have requested a non-existent parameter "locale"

Question

When I enable the 'dev' mode in my Symfony 4 app (that is already online in a shared hosting service) it shows this message:

(1/1) ParameterNotFoundException
You have requested a non-existent parameter "locale".

in ParameterBag.php (line 100)
at ParameterBag->get('locale')
in EnvPlaceholderParameterBag.php (line 57)
at EnvPlaceholderParameterBag->get('locale')
in ParameterBag.php (line 216)
at ParameterBag->resolveString('%locale%', array('locale' => true))
in ParameterBag.php (line 187)
...

and does not allow to debug the app. My config/services.yml code is as default:

# Put parameters here that don't need to change on each machine where the app is deployed
# https://symfony.com/doc/current/best_practices/configuration.html#application-related-configuration
parameters:
    locale: 'en'

services:
    # default configuration for Services in *this* file
    _defaults:
        autowire: true      # Automatically injects dependencies in your Services.
        autoconfigure: true # Automatically registers your Services as commands, event subscribers, etc.
        public: false       # Allows optimizing the container by removing unused Services; this also means
                            # fetching Services directly from the container via $container->get() won't work.
                            # The best practice is to be explicit about your dependencies anyway.
...

Please, someone can help me to fix this error.

Answer 1

Had the same problem during the fresh symfony 4.3 + sonata admin bundle installation. As a solution I added locale parameter:

// /config/services.yaml

parameters:
    locale: 'en'