pretty-env-logger = 0.2 fails to cargo doc

[richard-uk1]

This is caused by a dependency on different versions of the same crate, depending on target. See rust issue 49002. I made a small project to reproduce the problem on github.

I need to work out 2 things

1. How to fix it
2. How to write a regression test

I don't know how to write a test without using crates.io, because trying to depend on 2 different versions using a local path is rejected:

error: failed to parse manifest at `/home/rdodd/devel/non-work/rust_49002/Cargo.toml`

Caused by:
  Dependency 'dep' has different source paths depending on the build target. Each dependency must have a single canonical source path irrespective of build target.

Or maybe the manifest should fail to compile also for differing versions on crates.io?

[alexcrichton]

Thanks for the report! You can add crates to a registry in Cargo's test suite where it doesn't actually hit crates.io (search for usage of Package), and that may help in writing a test? Otherwise seems good to fix!