Fixes #3796: Deploy command continues despite composer failure

[nhmbounteous]

Fixes #3796

Changes proposed

Added logic check to see if the composer install command was successful, and if not interrupt the deployment to prevent corrupt environment code

Steps to replicate the issue

1. Create a semi-corrupt compsoer.json
2. Example, apply incorrect patch to module

"patches": {
    "drupal/svg_image_field": {
      "This doesn't apply": "https://www.drupal.org/files/issues/entity-browser-view-context-2865928-14.patch"
    },

3. Run blt artifact:deploy
4. The deployment will display the error [Exception] Cannot apply patch This doesn't apply (https://www.drupal.org/files/issues/entity-browser-view-context-2865928-14.patch)!
5. The error will be ignored and cause a broken artifact to be pushed to the environment.

Previous (bad) behavior, before applying PR

Corrupt environment code on deployment and ignored the composer error

Expected behavior, after applying PR and re-running test steps

An exception is now thrown and the process is stopped, preventing a corrupted artifact deployment

[josephdpurcell]

I would like to see this handle other cases. This only handles the composer case.

However, handling one case is better than none, and it addresses exactly #3796. Approving.

[danepowell]

Thanks a lot for the contribution. The code looks good (following the pattern used elsewhere in BLT) and I've verified that it fixes the issue.

This awaits one more internal review.

We will fix this more generally with a refactor in #3811

[alexxed]

Looks fine, but I wonder if Robo has something to automatically throw in these cases.

[danepowell]

@alexxed we are checking on that with the Robo maintainers here: consolidation/robo#891

But for now, it looks like no, Robo does not throw exceptions, it just provides an exit code.