The "http-get" test is sometimes failing because the Web server is not yet
initialized and returns the 500 error code.
Use the retry-or-error procedure, like in the tailon test to do a few retries.
* gnu/tests/web.scm (run-tailon-test): Move "retry-or-error" procedure to the
top level and adapt its call.
(run-patchwork-test): Use it.
3b5c4e6fb2