gh-md-toc fails silently with an empty toc on lack of network connectivity

[zeitounator]

Finally took the time to find out why I was getting empty tocs once in a while....

I move between my personal office and clients location where I'm frequently behind a proxy. I don't always set the outgoing proxy in my shell. It happens that gh-md-toc needs network connectivity, even to parse local file. But it fails silently with an empty toc in those cases. This is misleading.

This PR fixes this and fails with a message to check network connection, both for remote and local files.

[zeitounator]

Hi. I saw the travis test is failing. After having a closer and running the tests locally on the current master, it looks like it comes from the remote examples which changed structures. Should I fix this in this same PR ?

[ekalinin]

Hi @zeitounator

Thanks for the PR!

I saw the travis test is failing. After having a closer and running the tests locally on the current master, it looks like it comes from the remote examples which changed structures. Should I fix this in this same PR ?

No, you should not. It's not related to your changes.

[zeitounator]

@ekalinin My pleasure ! Thanks for your fast reaction.