Allow import Gitlab repo manually and set a webhook automatically

When we import a Project manually we don't have a RemoteRepository
associated with that Project, so we use the old technique of getting
the username and repo names from the URL using
`get_gitlab_username_repo` function.

This case (Manual Import) won't support custom Gitlab installations in
the future with this code.

readthedocs/oauth/services/gitlab.py

@@ -12,7 +12,9 @@
 from django.core.urlresolvers import reverse
 from requests.exceptions import RequestException
 
+from readthedocs.builds.utils import get_gitlab_username_repo
 from readthedocs.integrations.models import Integration
+from readthedocs.projects.models import Project
 
 from ..models import RemoteOrganization, RemoteRepository
 from .base import Service
@@ -41,6 +43,22 @@ class GitLabService(Service):
     url_pattern = re.compile(
         re.escape(urlparse(adapter.provider_base_url).netloc))
 
+    def _get_repo_id(self, project):
+        # The ID or URL-encoded path of the project
+        # https://docs.gitlab.com/ce/api/README.html#namespaced-path-encoding
+        try:
+            repo_id = json.loads(project.remote_repository.json).get('id')
+        except Project.remote_repository.RelatedObjectDoesNotExist:
+            # Handle "Manual Import" when there is no RemoteRepository
+            # associated with the project. It only works with gitlab.com at the
+            # moment (doesn't support custom gitlab installations)
+            username, repo = get_gitlab_username_repo(project.repo)
+            repo_id = '{username}%2F{repo}'.format(
+                username=username,
+                repo=repo,
+            )
+        return repo_id
+
     def get_next_url_to_paginate(self, response):
         return response.links.get('next', {}).get('url')
 
@@ -255,10 +273,7 @@ def setup_webhook(self, project):
             integration_type=Integration.GITLAB_WEBHOOK,
         )
 
-        # The ID or URL-encoded path of the project
-        # https://docs.gitlab.com/ce/api/README.html#namespaced-path-encoding
-        repo_id = json.loads(project.remote_repository.json).get('id')
-
+        repo_id = self._get_repo_id(project)
         data = self.get_webhook_data(repo_id, integration, project)
         resp = None
         try:
@@ -307,10 +322,7 @@ def update_webhook(self, project, integration):
         """
         session = self.get_session()
 
-        # The ID or URL-encoded path of the project
-        # https://docs.gitlab.com/ce/api/README.html#namespaced-path-encoding
-        repo_id = json.loads(project.remote_repository.json).get('id')
-
+        repo_id = self._get_repo_id(project)
         data = self.get_webhook_data(repo_id, project, integration)
         hook_id = integration.provider_data.get('id')
         resp = None