CMR across controllers

The following adds an example of consuming a model from another
controller that we also know about.

The helps with consuming CMR and the flakey nature of pylibjuju not
finding a model from the current model.

Author: SimonRichardson

examples/crossmodel_controller.py

@@ -0,0 +1,85 @@
+"""
+This example:
+
+1. Connects to test and test2 controllers
+2. Creates models on each controllers
+3. Deploys a charm and waits until it reports itself active
+4. Creates an offer
+5. Lists the offer
+6. Consumes the offer
+7. Exports the bundle
+8. Removes the SAAS
+9. Removes the offer
+10. Destroys models and disconnects
+"""
+import tempfile
+from logging import getLogger
+
+from juju import loop
+from juju.controller import Controller
+
+log = getLogger(__name__)
+
+
+async def main():
+    controller1 = Controller()
+    print("Connecting to controller")
+    await controller1.connect("test")
+
+    controller2 = Controller()
+    print("Connecting to controller")
+    await controller2.connect("test2")
+
+    try:
+        print('Creating models')
+        offering_model = await controller1.add_model('test-cmr-1')
+        consuming_model = await controller2.add_model('test-cmr-2')
+
+        print('Deploying mysql')
+        application = await offering_model.deploy(
+            'mysql',
+            application_name='mysql',
+            series='trusty',
+            channel='stable',
+        )
+
+        print('Waiting for active')
+        await offering_model.block_until(
+            lambda: all(unit.workload_status == 'active'
+                        for unit in application.units))
+
+        print('Adding offer')
+        await offering_model.create_offer("mysql:db")
+
+        offers = await offering_model.list_offers()
+        print('Show offers', ', '.join("%s: %s" % item for offer in offers.results for item in vars(offer).items()))
+
+        print('Consuming offer')
+        await consuming_model.consume("admin/test-cmr-1.mysql", controller_name="test")
+
+        print('Exporting bundle')
+        with tempfile.TemporaryDirectory() as dirpath:
+            await offering_model.export_bundle("{}/bundle.yaml".format(dirpath))
+
+        print("Remove SAAS")
+        await consuming_model.remove_saas("mysql")
+
+        print('Removing offer')
+        await offering_model.remove_offer("admin/test-cmr-1.mysql", force=True)
+
+        print('Destroying models')
+        await controller1.destroy_model(offering_model.info.uuid)
+        await controller2.destroy_model(consuming_model.info.uuid)
+
+    except Exception:
+        log.exception("Example failed!")
+        raise
+
+    finally:
+        print('Disconnecting from controller')
+        await controller1.disconnect()
+        await controller2.disconnect()
+
+
+if __name__ == '__main__':
+    loop.run(main())