Add dependency badge for Pipenv applications [GithubPipenv] (#4096)

I recently published https://github.com/metabolize/rq-dashboard-on-heroku and want to add badges to show the locked version of Python and rq-dashboard, the main dependency it’s wrapping.

This is along the lines of #2259, which was for package.json-based applications, and also included some discussion of a Python application that used `requirements.txt`. It’s useful for showing the pinned version of any dependency in a Python application that uses a lockfile.

In the future, as an alternative to reading Pipfile.lock, I could see expanding this to read Pipfile. However for my purposes I prefer to show the locked dependency, since that’s the version that a user of my package would actually get if they ran it on Heroku.

services/github/github-pipenv.tester.js

@@ -0,0 +1,93 @@
+'use strict'
+
+const Joi = require('@hapi/joi')
+const { ServiceTester } = require('../tester')
+const {
+  isVPlusDottedVersionAtLeastOne,
+  isVPlusDottedVersionNClausesWithOptionalSuffix,
+} = require('../test-validators')
+
+// e.g. v19.3b0
+const isBlackVersion = Joi.string().regex(/^v\d+(\.\d+)*(.*)?$/)
+const isShortSha = Joi.string().regex(/[0-9a-f]{7}/)
+
+const t = (module.exports = new ServiceTester({
+  id: 'GithubPipenv',
+  title: 'GithubPipenv',
+  pathPrefix: '/github/pipenv',
+}))
+
+t.create('Locked Python version')
+  .get('/locked/python-version/metabolize/rq-dashboard-on-heroku.json')
+  .expectBadge({
+    label: 'python',
+    message: isVPlusDottedVersionAtLeastOne,
+  })
+
+t.create('Locked Python version (no pipfile.lock)')
+  .get('/locked/python-version/metabolize/react-flexbox-svg.json')
+  .expectBadge({
+    label: 'python',
+    message: 'repo not found, branch not found, or Pipfile.lock missing',
+  })
+
+t.create('Locked Python version (pipfile.lock has no python version)')
+  .get('/locked/python-version/fikovnik/ShiftIt.json')
+  .expectBadge({
+    label: 'python',
+    message: 'version not specified',
+  })
+
+t.create('Locked version of default dependency')
+  .get(
+    '/locked/dependency-version/metabolize/rq-dashboard-on-heroku/rq-dashboard.json'
+  )
+  .expectBadge({
+    label: 'rq-dashboard',
+    message: isVPlusDottedVersionNClausesWithOptionalSuffix,
+  })
+
+t.create('Locked version of default dependency (branch)')
+  .get(
+    '/locked/dependency-version/metabolize/rq-dashboard-on-heroku/rq-dashboard/master.json'
+  )
+  .expectBadge({
+    label: 'rq-dashboard',
+    message: isVPlusDottedVersionNClausesWithOptionalSuffix,
+  })
+
+t.create('Locked version of dev dependency')
+  .get(
+    '/locked/dependency-version/metabolize/rq-dashboard-on-heroku/dev/black.json'
+  )
+  .expectBadge({
+    label: 'black',
+    message: isBlackVersion,
+  })
+
+t.create('Locked version of dev dependency (branch)')
+  .get(
+    '/locked/dependency-version/metabolize/rq-dashboard-on-heroku/dev/black/master.json'
+  )
+  .expectBadge({
+    label: 'black',
+    message: isBlackVersion,
+  })
+
+t.create('Locked version of unknown dependency')
+  .get(
+    '/locked/dependency-version/metabolize/rq-dashboard-on-heroku/dev/i-made-this-up.json'
+  )
+  .expectBadge({
+    label: 'dependency',
+    message: 'dev dependency not found',
+  })
+
+t.create('Locked version of VCS dependency')
+  .get(
+    '/locked/dependency-version/DemocracyClub/aggregator-api/dc-base-theme.json'
+  )
+  .expectBadge({
+    label: 'dc-base-theme',
+    message: isShortSha,
+  })