Updated app.py to make sure that images can start notebook servers

Includes an update of conftest.py file to check that the container
is running with jupyter notebook in all the builders.

repo2docker/app.py

@@ -103,10 +103,10 @@ class Repo2Docker(Application):
 
         Use a key-value pair, with the key being the volume source &
         value being the destination volume.
-        
-        Both source and destination can be relative. Source is resolved 
+
+        Both source and destination can be relative. Source is resolved
         relative to the current working directory on the host, and
-        destination is resolved relative to the working directory of the 
+        destination is resolved relative to the working directory of the
         image - ($HOME by default)
         """,
         config=True
@@ -504,7 +504,7 @@ class Repo2Docker(Application):
         client = docker.from_env(version='auto')
         if not self.run_cmd:
             port = str(self._get_free_port())
-
+            self.port = port
             run_cmd = ['jupyter', 'notebook', '--ip', '0.0.0.0',
                        '--port', port]
             ports = {'%s/tcp' % port: port}

tests/conftest.py

@@ -11,6 +11,8 @@ success.
 import os
 import pipes
 import shlex
+import requests
+import time
 
 import pytest
 import yaml
@@ -30,7 +32,39 @@ def make_test_func(args):
     def test():
         app = Repo2Docker()
         app.initialize(args)
-        app.start()
+        if app.run_cmd:
+            # verify test, run it
+            app.start()
+            return
+        # no run_cmd given, starting notebook server
+        app.run = False
+        app.start()  # This just build the image and does not run it.
+        container = app.start_container()
+        port = app.port
+        # wait a bit for the container to be ready
+        container_url = 'http://localhost:%s/api' % port
+        # give the container a chance to start
+        time.sleep(1)
+        try:
+            # try a few times to connect
+            success = False
+            for i in range(1, 4):
+                container.reload()
+                assert container.status == 'running'
+                try:
+                    info = requests.get(container_url).json()
+                except Exception as e:
+                    print("Error: %s" % e)
+                    time.sleep(i * 3)
+                else:
+                    print(info)
+                    success = True
+                    break
+            assert success, "Notebook never started in %s" % container
+        finally:
+            # stop the container
+            container.stop()
+            app.wait_for_container(container)
     return test
 
 
@@ -68,6 +102,13 @@ class LocalRepo(pytest.File):
                 './verify',
             ],
         )
+        yield Repo2DockerTest(
+            self.fspath.basename, self,
+            args=[
+                '--appendix', 'RUN echo "appendix" > /tmp/appendix',
+                self.fspath.dirname,
+            ],
+        )
 
 
 class RemoteRepoList(pytest.File):