environment_spec.rb

In EE we redefine Environment#terminals, which makes it impossible to
use `allow_any_instance_of(Environment)` or
`expect_any_instance_of(Environment)`. Other approaches of stubbing
this class, such as by stubbing `new`, only result in spec failures.

To solve this issue, we add a simple `defined?(EE)` check in the tests
to change the thing that we are testing. This is rather obnoxious,
because it requires EE knowledge in CE, and can break if
`EE::Environment` is removed without updating CE. Unfortunately, it
appears to be the only solution we have apart from modifying these tests
in EE (which would cause merge conflicts).