Confusing error message - Concerto CLI

[4katie]

Is your feature request related to a problem? Please describe.
The error message that appears when I enter incorrect commands are confusing and quite generic.

hyewon@hobbang:~/Accord_Project/cicero-template-library/src/latedeliveryandpenalty$ concerto validate 
15:13:21 - error: ENOENT: no such file or directory, open 'sample.json'

hyewon@hobbang:~/Accord_Project/cicero-template-library/src/latedeliveryandpenalty$ concerto compile
15:13:29 - error: EISDIR: illegal operation on a directory, read

hyewon@hobbang:~/Accord_Project/cicero-template-library/src/latedeliveryandpenalty$ concerto get
15:13:32 - error: EISDIR: illegal operation on a directory, read

hyewon@hobbang:~/Accord_Project/cicero-template-library/src/latedeliveryandpenalty/models$ concerto compile clause.cto --target Go
15:13:41 - error: EISDIR: illegal operation on a directory, read

Describe the solution you'd like
More informative error messages.

For example, this error message (when I used a wrong .json file) was quite helpful:

hyewon@hobbang:~/Accord_Project/cicero-template-library/src/latedeliveryandpenalty$ concerto validate --sample package.json --ctoFiles models/clause.cto
15:10:08 - error: Invalid JSON data. Does not contain a $class type identifier.

For the code snippet above, for example concerto compile clause.cto --target Go, an error message could be something like:

error: target CTO file unclear. 
Try including --ctoFiles in front of the target CTO files you want to convert

or a more generic, but more specific, error message (compared to EISDIR) would be:

error: cannot find command arguments. 
Try using `concerto compile --ctoFiles <filename> --target <targetFormat>`

Describe alternatives you've considered
N/A

Additional context
concerto version 0.82.4

[jeromesimeon]

With upcoming PR in #155

bash-3.2$ ~/git/concerto/packages/concerto-cli/index.js get 
concerto get

save local copies of external model dependencies

Options:
  --version      Show version number                                   [boolean]
  --verbose, -v                                                 [default: false]
  --help         Show help                                             [boolean]
  --ctoFiles     array of local CTO files                     [array] [required]
  --ctoSystem    system model to be used                                [string]
  --output       output directory path                  [string] [default: "./"]

Missing required argument: ctoFiles
Please provide at least the CTO files
bash-3.2$ ~/git/concerto/packages/concerto-cli/index.js validate 
13:46:39 - info: Loading a default sample.json file.
13:46:39 - error: A sample.json file is required. Try the --sample flag or create a sample.json file.
bash-3.2$ ~/git/concerto/packages/concerto-cli/index.js compile
concerto compile

generate code for a target platform

Options:
  --version      Show version number                                   [boolean]
  --verbose, -v                                                 [default: false]
  --help         Show help                                             [boolean]
  --ctoSystem    system model to be used                                [string]
  --ctoFiles     array of CTO files                           [array] [required]
  --target       target of the code generation  [string] [default: "JSONSchema"]
  --output       output directory path           [string] [default: "./output/"]

Missing required argument: ctoFiles
Please provide at least the CTO files