emit error message when socket creation fails

[auerswal]

This is the patch from my comment on issue 201, but now I have tested it, and it works, at least for me. :-)

To test, I have temporarily changed the requested protocol name to something nonsensical. With the patch, an error message was emitted, but not without the patch.

I think a pull request like this was requested in a comment on issue 201.

My PR 250 (distinguish ICMP and ICMP6 in error messages) makes this error message more useful.

[coveralls]

Coverage remained the same at 78.596% when pulling 2a6c82266b057ab80176067be9aae511571efc34 on auerswal:sock-err-vis into ab1ed993badc1a6978b95c9d17a5e8b56fff4598 on schweikert:develop.

[auerswal]

Is there any interest in this work?

[auerswal]

Closing this pull request due to lack of interest in this work.