Handle :error when sending test event

[mitchellhenke]

Closes #226

New output will look something like this if the test event fails to send:

Sending test event...

19:35:30.170 [warn]  Failed to send Sentry event.
{:error, :nxdomain}
{"user":{},"timestamp":"2017-11-10T01:35:30","tags":{"env":"production"},"server_name":"Mitchells-MacBook-Pro.local","request":{},"release":null,"platform":"elixir","modules":{"uuid":"1.1.7","ssl_verify_fun":"1.1.1","poison":"2.2.0","plug":"1.2.3","mimerl":"1.0.2","mime":"1.1.0","metrics":"1.0.1","hackney":"1.6.5"},"message":"(RuntimeError) Testing sending Sentry event","level":"error","fingerprint":["{{ default }}"],"extra":{},"exception":[{"value":"Testing sending Sentry event","type":"Elixir.RuntimeError","module":null}],"event_id":"6910c421e7f74881a8e7cc3c37795434","environment":"dev","culprit":null,"breadcrumbs":[]}

19:35:32.173 [warn]  Failed to send Sentry event.
{:error, :nxdomain}
{"user":{},"timestamp":"2017-11-10T01:35:30","tags":{"env":"production"},"server_name":"Mitchells-MacBook-Pro.local","request":{},"release":null,"platform":"elixir","modules":{"uuid":"1.1.7","ssl_verify_fun":"1.1.1","poison":"2.2.0","plug":"1.2.3","mimerl":"1.0.2","mime":"1.1.0","metrics":"1.0.1","hackney":"1.6.5"},"message":"(RuntimeError) Testing sending Sentry event","level":"error","fingerprint":["{{ default }}"],"extra":{},"exception":[{"value":"Testing sending Sentry event","type":"Elixir.RuntimeError","module":null}],"event_id":"6910c421e7f74881a8e7cc3c37795434","environment":"dev","culprit":null,"breadcrumbs":[]}

19:35:36.175 [warn]  Failed to send Sentry event.
{:error, :nxdomain}
{"user":{},"timestamp":"2017-11-10T01:35:30","tags":{"env":"production"},"server_name":"Mitchells-MacBook-Pro.local","request":{},"release":null,"platform":"elixir","modules":{"uuid":"1.1.7","ssl_verify_fun":"1.1.1","poison":"2.2.0","plug":"1.2.3","mimerl":"1.0.2","mime":"1.1.0","metrics":"1.0.1","hackney":"1.6.5"},"message":"(RuntimeError) Testing sending Sentry event","level":"error","fingerprint":["{{ default }}"],"extra":{},"exception":[{"value":"Testing sending Sentry event","type":"Elixir.RuntimeError","module":null}],"event_id":"6910c421e7f74881a8e7cc3c37795434","environment":"dev","culprit":null,"breadcrumbs":[]}

19:35:44.179 [warn]  Failed to send Sentry event.
{:error, :nxdomain}
{"user":{},"timestamp":"2017-11-10T01:35:30","tags":{"env":"production"},"server_name":"Mitchells-MacBook-Pro.local","request":{},"release":null,"platform":"elixir","modules":{"uuid":"1.1.7","ssl_verify_fun":"1.1.1","poison":"2.2.0","plug":"1.2.3","mimerl":"1.0.2","mime":"1.1.0","metrics":"1.0.1","hackney":"1.6.5"},"message":"(RuntimeError) Testing sending Sentry event","level":"error","fingerprint":["{{ default }}"],"extra":{},"exception":[{"value":"Testing sending Sentry event","type":"Elixir.RuntimeError","module":null}],"event_id":"6910c421e7f74881a8e7cc3c37795434","environment":"dev","culprit":null,"breadcrumbs":[]}
Error sending event!

Thanks to @jalcine for reporting this issue 🙂