`snyk/actions/setup` seems flakey, errors with `No URLs found in -.`

[rtyley]

The Synk Github Action we use in many of our repos seems flakey? https://github.com/guardian/play-secret-rotation/actions/workflows/snyk.yml has failed spuriously twice in the past 24 hours:

The error occurs in the Run snyk/actions/setup step, which is configured in this repo here:

.github/.github/workflows/sbt-node-snyk.yml

Lines 71 to 77 in cda5bbb

	security:
	runs-on: ubuntu-latest
	steps:
	- name: Checkout branch
	uses: actions/checkout@v2
	- uses: snyk/actions/setup@0.3.0

The error on an unsuccessful run is:

Installing the latest version of Snyk on Linux
No URLs found in -.
sha256sum: snyk-linux.sha256: No such file or directory
Error: Process completed with exit code 1.

A successful run would differ at the No URLs found in -. line, and say:

Installing the latest version of Snyk on Linux
--2023-01-12 10:40:47--  https://github.com/snyk/cli/releases/download/v1.10[8](https://github.com/guardian/play-secret-rotation/actions/runs/3901451722/jobs/6663316114#step:3:10)5.0/snyk-linux
Resolving github.com (github.com)... 140.82.112.3
Connecting to github.com (github.com)|140.82.112.3|:443... connected.
HTTP request sent, awaiting response... 302 Found

The workaround is to re-run the job - it will normally pass on the 2nd try.

Cause

The first line that's obviously failing is the first wget in setup_snyk.sh. We see the error message No URLs found in -., and that's an error message generated by wget:

  /* And then from the input file, if any.  */
  if (opt.input_filename)
    {
      int count;
      int status;
      status = retrieve_from_file (opt.input_filename, opt.force_html, &count);
      inform_exit_status (status);
      if (!count)
        logprintf (LOG_NOTQUIET, _("No URLs found in %s.\n"),
                   opt.input_filename);
    }

The wget is trying to do this:

wget --progress=bar:force:noscroll "$BASE_URL/$VERSION/snyk-${PREFIX}"