CI Error with ElixirPetstoreClientTests on shippable

Created by: jmini

https://app.shippable.com/github/OpenAPITools/openapi-generator/runs/94/1/console

[INFO] ------------------------------------------------------------------------
[INFO] Building Elixir Petstore Client 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.8:copy-dependencies (default) @ ElixirPetstoreClientTests ---
[INFO] 
[INFO] --- exec-maven-plugin:1.2.1:exec (dep-install) @ ElixirPetstoreClientTests ---
* creating /root/.mix/archives/hex.ez
[INFO] 
[INFO] --- exec-maven-plugin:1.2.1:exec (compile) @ ElixirPetstoreClientTests ---
Resolving Hex dependencies...
Dependency resolution completed:
New:
  mime 1.2.0
  poison 3.1.0
  tesla 0.10.0
All dependencies up to date
** (Mix) You're trying to run :openapi_petstore on Elixir v1.1.0-dev but it has declared in its mix.exs file it supports only Elixir ~> 1.4

---

I have tried locally:

mvn verify -f samples/client/petstore/elixir/pom.xml

But this requires the mix program.