Configuration is evaluated on container declaration when using Container provider

[Qjammer]

Configuration provider will throw ValueError: Missing required environment variable "MYENV" when declaring a container that uses another container as a dependency. The following snippet exemplifies the behavior:

# test.yaml
a: "${MYENV}"

# main.py
class A(containers.DeclarativeContainer):
    config = providers.Configuration(strict=True, yaml_files=["./test.yaml"])

# Commenting out these two lines does not throw
class B(containers.DeclarativeContainer):
    a = providers.Container(A) # Throws ValueError: Missing required environment variable "MYENV"

# Anything after this does not matter.

Expected behavior: The script doesn't throw an exception until the container is instantiated.