tweak un-installed connector error message

[seanbrookes]

see #346

• the server responsds with whatever exceptions are on the stack regardless of UI context so can sometimes be confusing.
• in this case we are concerned about datasource connectors being referenced but not installed causing exceptions to be displayed in odd contexts.
• the real fix is out of scope for R2 so for now we are going to tweak the message from loopback-datasource-juggler to give the user a little more context

[seanbrookes]

note the fix for this is in loopback-datasource-juggler https://github.com/strongloop/loopback-datasource-juggler/pull/315

[altsang]

what's confusing in this scenarios is that when you trigger validation by testing connection on one datasource , you're getting back an error on another datasource because of the connector initialization process, we'll deal with this post R2, for now have asked @crandmck to doc

[frankcarey]

This would be helpful.. I've been pulling my hair out trying to understand why I was getting errors from mongo instead of rest connector and I'm assuming this is the cause. Also shouldn't the start fail completely instead of just a warning if a connector is missing?

// Currently (my version of code) it just outputs a warning and drives on.
if (!connector) {
    error = util.format('\nWARNING: LoopBack connector "%s" is not installed ' +
      'as any of the following modules:\n\n %s\n\nTo fix, run:\n\n    npm install %s\n',
      name, names.join('\n'), names[names.length -1]);
  }

[bajtos]

Also shouldn't the start fail completely instead of just a warning if a connector is missing?

Could you please fill an issue in loopback for this?

[frankcarey]

The request was added to https://github.com/strongloop/loopback-datasource-juggler/issues/320