Provide a more friendly message on 401

[pedrocunha]

The tool should not blow up on invalid credentials:

$ elba list
/Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/excon-0.44.4/lib/excon/middlewares/expects.rb:6:in `response_call': InvalidClientTokenId => The security token included in the request is invalid. (Fog::AWS::ELB::Error)
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/excon-0.44.4/lib/excon/middlewares/response_parser.rb:8:in `response_call'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/excon-0.44.4/lib/excon/connection.rb:372:in `response'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/excon-0.44.4/lib/excon/connection.rb:236:in `request'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-xml-0.1.1/lib/fog/xml/sax_parser_connection.rb:37:in `request'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-xml-0.1.1/lib/fog/xml/connection.rb:7:in `request'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-aws-0.1.1/lib/fog/aws/elb.rb:198:in `_request'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-aws-0.1.1/lib/fog/aws/elb.rb:193:in `request'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-aws-0.1.1/lib/fog/aws/requests/elb/describe_load_balancers.rb:61:in `describe_load_balancers'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-aws-0.1.1/lib/fog/aws/models/elb/load_balancers.rb:18:in `all'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-core-1.29.0/lib/fog/core/collection.rb:113:in `lazy_load'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/fog-core-1.29.0/lib/fog/core/collection.rb:17:in `size'
    from /Users/pedrocunha/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/elba-0.0.5/lib/elba/cli.rb:66:in `list'

Maybe worth to catch this exception and provide a better message ?

[mrship]

You get a slightly more friendly error with the latest version with upgraded gems that points to the root cause.

➜  bin/elba list       
Digest::Digest is deprecated; use Digest
/Users/mrship/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/excon-0.23.0/lib/excon/middlewares/expects.rb:6:in `response_call': Expected(200) <=> Actual(403 Forbidden) (Excon::Errors::Forbidden)
  response => #<Excon::Response:0x007f8e232c9620 @data={:body=>"<ErrorResponse xmlns=\"http://elasticloadbalancing.amazonaws.com/doc/2012-06-01/\">\n  <Error>\n    <Type>Sender</Type>\n    <Code>InvalidClientTokenId</Code>\n    <Message>The security token included in the request is invalid</Message>\n

Given all other errors also raise - missing credentials, other Fog errors etc. - I think an overhaul of the errors would be needed.

[pedrocunha]

I still think we could try to progressively rescue some of the errors and provide better error messages