feat(api): Allow using an unreleased image

This is useful for build steps which must be completed before an app is fully
deployed to deis, for example asset compilation.

rootfs/api/models/app.py

@@ -684,7 +684,7 @@ def logs(self, log_lines=str(settings.LOG_LINES)):
         # cast content to string since it comes as bytes via the requests object
         return str(r.content.decode('utf-8'))
 
-    def run(self, user, command):
+    def run(self, user, command, image=None):
         def pod_name(size=5, chars=string.ascii_lowercase + string.digits):
             return ''.join(random.choice(chars) for _ in range(size))
 
@@ -695,7 +695,8 @@ def pod_name(size=5, chars=string.ascii_lowercase + string.digits):
 
         app_settings = self.appsettings_set.latest()
         # use slugrunner image for app if buildpack app otherwise use normal image
-        image = settings.SLUGRUNNER_IMAGE if release.build.type == 'buildpack' else release.image
+        if image is None:
+            image = settings.SLUGRUNNER_IMAGE if release.build.type == 'buildpack' else release.image
 
         data = self._gather_app_settings(release, app_settings, process_type='run', replicas=1)
 

rootfs/api/views.py

@@ -238,7 +238,7 @@ def run(self, request, **kwargs):
         app = self.get_object()
         if not request.data.get('command'):
             raise DeisException("command is a required field")
-        rc, output = app.run(self.request.user, request.data['command'])
+        rc, output = app.run(self.request.user, request.data['command'], image=request.data.get('image'))
         return Response({'exit_code': rc, 'output': str(output)})
 
     def update(self, request, **kwargs):