Unit test cases break when elixir version upgraded from 1.7.2 to 1.8.0

Hello,

I am a newbie in Elixir-Phoenix. I have an application where the unit test cases were written using ExUnit and mock 0.3.0. The test cases were working fine with Elixir 1.7.2. However, all the test cases are now breaking when I upgraded Elixir version to 1.8.0 with the following error-
** (ErlangError) Erlang error: {:compile_forms, {:error, [{, [{:none, :compile, {:crash, :sys_core_fold, {{:case_clause, {:EXIT, {:function_clause, [{:sys_core_fold, :module, [[{:attribute, 1, :file,…

Here are my dependencies for reference-
{:phoenix, “~> 1.3.1”},
{:phoenix_ecto, “~> 3.2”},
{:mariaex, “~> 0.8.4”},
{:gettext, “~> 0.11”},
{:cowboy, “~> 1.0”},
{:credo, “~> 0.9.1”, only: [:dev, :test], runtime: false},
{:mock, “~> 0.3.0”, only: :test},
{:uuid, “~> 1.1”},
{:ex_aws, “~> 2.0”},
{:ex_aws_s3, “~> 2.0”},
{:hackney, “~> 1.9”},
{:sweet_xml, “~> 0.6”},
{:httpoison, “~> 1.0”},
{:exvcr, “~> 0.10”, only: :test}

The corresponding Erlang/OTP version is 21.
I searched for this kind of issue but no luck so far. Any help would be greatly appreciated.

FYI: The application works fine, the problem is the test cases.

Thanks in advance.