Use configured github server in app mode

Currently when running as github app the urls for the api access are
hard coded to github.com. We need to use the configured github server
for this if we want to use apps for github enterprise.

Change-Id: I9b98d45f37d7cb6842c95cdce6435b86d33e924d

zuul/driver/github/githubconnection.py

@@ -38,10 +38,8 @@ from zuul.model import Ref, Branch, Tag, Project
 from zuul.exceptions import MergeFailure
 from zuul.driver.github.githubmodel import PullRequest, GithubTriggerEvent
 
-ACCESS_TOKEN_URL = 'https://api.github.com/installations/%s/access_tokens'
+GITHUB_BASE_URL = 'https://api.github.com'
 PREVIEW_JSON_ACCEPT = 'application/vnd.github.machine-man-preview+json'
-INSTALLATIONS_URL = 'https://api.github.com/app/installations'
-REPOS_URL = 'https://api.github.com/installation/repositories'
 
 
 def _sign_request(body, secret):
@@ -415,6 +413,11 @@ class GithubConnection(BaseConnection):
         self.source = driver.getSource(self)
         self.event_queue = queue.Queue()
 
+        if self.server == 'github.com':
+            self.base_url = GITHUB_BASE_URL
+        else:
+            self.base_url = 'https://%s/api/v3' % self.server
+
         # ssl verification must default to true
         verify_ssl = self.connection_config.get('verify_ssl', 'true')
         self.verify_ssl = True
@@ -546,7 +549,10 @@ class GithubConnection(BaseConnection):
 
         if ((not expiry) or (not token) or (now >= expiry)):
             headers = self._get_app_auth_headers()
-            url = ACCESS_TOKEN_URL % installation_id
+
+            url = "%s/installations/%s/access_tokens" % (self.base_url,
+                                                         installation_id)
+
             json_data = {'user_id': user_id} if user_id else None
 
             response = requests.post(url, headers=headers, json=json_data)
@@ -568,7 +574,8 @@ class GithubConnection(BaseConnection):
         if not self.app_id:
             return
 
-        url = INSTALLATIONS_URL
+        url = '%s/app/installations' % self.base_url
+
         headers = self._get_app_auth_headers()
         self.log.debug("Fetching installations for GitHub app")
         response = requests.get(url, headers=headers)
@@ -581,7 +588,9 @@ class GithubConnection(BaseConnection):
             token = self._get_installation_key(project=None, inst_id=inst_id)
             headers = {'Accept': PREVIEW_JSON_ACCEPT,
                        'Authorization': 'token %s' % token}
-            url = REPOS_URL
+
+            url = '%s/installation/repositories' % self.base_url
+
             self.log.debug("Fetching repos for install %s" % inst_id)
             response = requests.get(url, headers=headers)
             response.raise_for_status()