Log errors and exit on authentication issues on Hubot plugin initialization

[jinpingh]

Fixes StackStorm/st2chatops#124

1. Capture all authentication related exceptions and exit from st2chatops.
2. Create new callback function for robot.error to capture uncaught error from hubot.
3. Add unit tests for authentication error.

Closes StackStorm/st2tests#170

[arm4b]

I find the fact that we need introducing ENV variable like EXIT_ON_FAILURES a bad sign.

It's an expected practice for an app to exit if there is a critical error we can't recover from.
Otherwise what value brings the daemon which prints single Failed to authenticate: error message and going into a waiting behavior?

If we talk about the failure which could be potentially recovered by connection retries/or retries with backoff, - we can consider using that instead. But if nothing helped, - always exit with error message and non-zero exit code.

[blag]

If we talk about the failure which could be potentially recovered by connection retries/or retries with backoff, - we can consider using that instead.

We have this behavior between other microservices of ST2, so it would be nice to have the same behavior in st2chatops. But code-wise, it would be frustrating to keep the semantics of "retry with backoff" in st2chatops up-to-date with how it works in the rest of ST2.

But if nothing helped, - always exit with error message and non-zero exit code.

This is the easiest thing for us to do. At this point, I think this behavior is a good compromise between trying to behave like the other ST2 services and increased complexity of this codebase/PR.

[blag]

@armab Sorry to keep pulling you back to this, but I figured out how to test this all, and I think it's finally in a mergeable state!

[blag]

Coverage from current master:

------------------------|----------|----------|----------|----------|-------------------|
File                    |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
------------------------|----------|----------|----------|----------|-------------------|
All files               |    82.73 |    79.59 |    83.76 |    82.24 |                   |
 lib                    |    96.88 |    96.68 |    97.75 |    96.75 |                   |
  command_factory.js    |      100 |      100 |      100 |      100 |                   |
  format_command.js     |      100 |      100 |      100 |      100 |                   |
  format_data.js        |      100 |      100 |      100 |      100 |                   |
  post_data.js          |      100 |      100 |      100 |      100 |                   |
  slack-messages.js     |    88.89 |    81.58 |    91.67 |    87.64 |... 34,35,37,38,43 |
  slack_monkey_patch.js |    28.57 |       80 |       50 |    28.57 |    17,18,19,28,29 |
  utils.js              |      100 |      100 |      100 |      100 |                   |
 scripts                |    41.81 |    37.11 |    39.29 |    41.81 |                   |
  stackstorm.js         |    41.81 |    37.11 |    39.29 |    41.81 |... 04,405,406,431 |
------------------------|----------|----------|----------|----------|-------------------|

Coverage from this branch:

------------------------|----------|----------|----------|----------|-------------------|
File                    |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
------------------------|----------|----------|----------|----------|-------------------|
All files               |     87.9 |    86.34 |    86.67 |    87.56 |                   |
 lib                    |       99 |    99.57 |    98.86 |    98.96 |                   |
  command_factory.js    |      100 |      100 |      100 |      100 |                   |
  format_command.js     |      100 |      100 |      100 |      100 |                   |
  format_data.js        |      100 |      100 |      100 |      100 |                   |
  post_data.js          |      100 |      100 |      100 |      100 |                   |
  slack-messages.js     |      100 |      100 |      100 |      100 |                   |
  slack_monkey_patch.js |    28.57 |       80 |       50 |    28.57 |    17,18,19,40,41 |
  utils.js              |      100 |      100 |      100 |      100 |                   |
 scripts                |    59.28 |    58.56 |    53.13 |    59.28 |                   |
  stackstorm.js         |    59.28 |    58.56 |    53.13 |    59.28 |... 96,425,461,462 |
------------------------|----------|----------|----------|----------|-------------------|

👍