adapter Ecto.Adapters.Postgres was not compiled : <p>I am not able to create my Phoenix project. Would love some advice on how to fix it.</p>

<p>Setup details:</p>

<ul>
<li>Ubuntu 16.04.4 LTS </li>
<li>Erlang/OTP 21 [erts-10.1] [source] [64-bit]
[smp:1:1] [ds:1:1:10] [async-threads:1] [hipe] </li>
<li>Elixir 1.7.3 (compiled
with Erlang/OTP 20)</li>
<li>Mix 1.7.3 (compiled with Erlang/OTP 20)</li>
<li>Ecto v3.0.0</li>
</ul>

<p>I am following the <a href="https://hexdocs.pm/phoenix/up_and_running.html#content" rel="noreferrer">Phoenix Up and Running</a> to make an app. </p>

<pre><code>mix phx.new hello
cd hello
mix ecto.create
</code></pre>

<p>last command gives me:</p>

<pre><code> == Compilation error in file lib/hello/repo.ex ==
 ** (ArgumentError) adapter Ecto.Adapters.Postgres was not compiled, ensure it is correct and it is included as a project dependency
     lib/ecto/repo/supervisor.ex:71: Ecto.Repo.Supervisor.compile_config/2
     lib/hello/repo.ex:2: (module)
     (stdlib) erl_eval.erl:680: :erl_eval.do_apply/6
     (elixir) lib/kernel/parallel_compiler.ex:206: anonymous fn/4 in Kernel.ParallelCompiler.spawn_workers/6
</code></pre>

<p>I have postgres installed. I have postgres super user. </p>
