Failed to use "poison" (version 3.1.0) because

[iSuslov]

My deps look like this:

  defp deps do
    [cowboy: "~> 1.0",
    plug: "~> 1.0",
    poison: "~> 3.1",
    execjs: "~> 1.1.3"]
  end

when I try deps.get I'm getting

mix deps.get
Running dependency resolution...

Failed to use "poison" (version 3.1.0) because
  execjs (version 1.1.3) requires ~> 1.5
  mix.lock specifies 3.1.0

** (Mix) Hex dependency resolution failed, relax the version requirements of your dependencies or unlock them (by using mix deps.update or mix deps.unlock). If you are unable to resolve the conflicts you can try overriding with {:dependency, "~> 1.0", override: true}

[iSuslov]

workaround for me was:

{:execjs, git: "https://github.com/devinus/execjs.git", tag: "a1c0af4c3b0afc9d6f176bf82f9c5b9fae3f2a45"}]

in deps

[yjukaku]

I think the best thing would be to just add override: true in your deps {:poison, "~> 3.1.0", override: true}

[KimSien]

check readme.md

https://github.com/trenpixster/addict

1a - Note that mailgun locks Poison to an old 1.4 version, which may cause conflicts (Poison). There's > a fix in place that just hasn't been pushed to hex. Resolve by also adding to your dependencies:

{:mailgun, github: "chrismccord/mailgun", branch: "master", override: true}