Add tests to the error handling when using multiple endpoints

[chaodhib]

This PR is a minor follow up to #544. I thought it would be better to add those 2 tests to the error handling

[josevalim]

I pushed a small change to the error message, can you please rebase and update your tests? Thanks!

[chaodhib]

Sure, done

[josevalim]

I don't think those need to be regexes, as using a string will also be a submatch. Can we use strings instead? They should be easier to read. :) Thanks!

[chaodhib]

Indeed. done :)

[chaodhib]

Here is the current output:

** (Postgrex.Error) failed to establish connection to multiple endpoints:

  * doesntexist:5432: (DBConnection.ConnectionError) tcp connect (doesntexist:5432): non-existing domain - :nxdomain
  * localhost:5555: (DBConnection.ConnectionError) tcp connect (localhost:5555): connection refused - :econnrefused
    (db_connection 2.1.0) lib/db_connection/connection.ex:87: DBConnection.Connection.connect/2
    (connection 1.0.4) lib/connection.ex:622: Connection.enter_connect/5
    (stdlib 3.11) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

Is the double newline character after "multiple endpoints:" intended? Wouldn't one newline be enough?

[josevalim]

@chaodhib it is intentional, most Elixir exceptions use that standard. :)

[chaodhib]

@josevalim good to know. thank you :)