#88 at skycoin/skywire. Return 400 with appropriate message

[kostyaVyrodov]

I've found an issue #88 in the skycoin/skywire repository and I tried to fix it.

This pull request modifies the error message of the UpdatePass function. I've added some code that returns the status code and error message to a user.

Please, let me know if I should update something else in the code base of skycoin/net repo to make the fix complete.

[gz-c]

Can you submit the PR to github.com/skycoin/skywire? We just moved this code into that repo, under the pkg/ folder

[CLAassistant]

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