There are two fixes here:
* All dependencies run in a particular environment, which defaults
to prod. If two dependencies have different environments, they
will diverge but the error message wouldn't include the env flag,
which made it hard to spot the reason. This commit now always
include the :env option
* Our converger algorithm was comparing [env: :prod] with [] and
accusing a divergence but they should be the same as the default
:env is :prod. We have made sure to set the environment to :prod
for all deps
José Valim
eced1303ef