- look for the --env and --no-debug only before a -- separator, to respect
the support for --
- avoid passing an empty string as parameter option name (which would never
match anyway, but causes php warning is some Symfony versions instead of
being ignored silently).
`composer install --no-dev` fails when Dotenv is a dev dependency (which
it is in skeleton) and you're running in an environment without an
APP_ENV variable set.
Throw exception when no env variables are set and Dotenv is absent so
the user knows to either require DotEnv or specify an APP_ENV variable.