Fix github dependent pipeline with merge

When enabling merge in a github gate pipeline merge message formatting
fails with an exception [1]. The reason for this is a missing
initialization of the GithubUser data structure which is using lazy
initialization (presumibly due to api rate limiting). This is fixed by
adding the initialization.

This was uncovered in the tests because the FakeGithubConnection
directly returns a data structure instead of a GithubUser object like
the real GithubConnection. This is fixed by returning a real
GithubUser object linked to a FakeGithub object.

[1] 2017-08-02 07:13:21,323 ERROR zuul.DependentPipelineManager: Exception while reporting:
  Traceback (most recent call last):
    File "/usr/lib/python3.6/site-packages/zuul/manager/__init__.py", line 786, in _reportItem
      ret = self.sendReport(actions, item)
    File "/usr/lib/python3.6/site-packages/zuul/manager/__init__.py", line 168, in sendReport
      ret = reporter.report(item)
    File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubreporter.py", line 73, in report
      self.mergePull(item)
    File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubreporter.py", line 129, in mergePull
      message = self._formatMergeMessage(item.change)
    File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubreporter.py", line 168, in _formatMergeMessage
      if not account:
    File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 340, in __len__
      return len(self._data)
  TypeError: object of type 'NoneType' has no len()

Change-Id: Ieb9694ff0c98c8cc4011cd4e36627e8ed647d078

tests/base.py

@@ -551,6 +551,18 @@ class GithubChangeReference(git.Reference):
     _points_to_commits_only = True
 
 
+class FakeGithub(object):
+
+    class FakeUser(object):
+        def __init__(self, login):
+            self.login = login
+            self.name = "Github User"
+            self.email = "github.user@example.com"
+
+    def user(self, login):
+        return self.FakeUser(login)
+
+
 class FakeGithubPullRequest(object):
 
     def __init__(self, github, number, project, branch,
@@ -879,6 +891,13 @@ class FakeGithubConnection(githubconnection.GithubConnection):
         self.merge_failure = False
         self.merge_not_allowed_count = 0
         self.reports = []
+        self.github_client = FakeGithub()
+
+    def getGithubClient(self,
+                        project=None,
+                        user_id=None,
+                        use_app=True):
+        return self.github_client
 
     def openFakePullRequest(self, project, branch, subject, files=[],
                             body=None):
@@ -965,14 +984,6 @@ class FakeGithubConnection(githubconnection.GithubConnection):
         pr = self.pull_requests[number - 1]
         return pr.reviews
 
-    def getUser(self, login):
-        data = {
-            'username': login,
-            'name': 'Github User',
-            'email': 'github.user@example.com'
-        }
-        return data
-
     def getRepoPermission(self, project, login):
         owner, proj = project.split('/')
         for pr in self.pull_requests:

zuul/driver/github/githubconnection.py

@@ -326,25 +326,26 @@ class GithubUser(collections.Mapping):
         self._data = None
 
     def __getitem__(self, key):
-        if self._data is None:
+        self._init_data()
-            self._data = self._init_data()
         return self._data[key]
 
     def __iter__(self):
+        self._init_data()
         return iter(self._data)
 
     def __len__(self):
+        self._init_data()
         return len(self._data)
 
     def _init_data(self):
+        if self._data is None:
             user = self._github.user(self._username)
             log_rate_limit(self.log, self._github)
-        data = {
+            self._data = {
                 'username': user.login,
                 'name': user.name,
                 'email': user.email
             }
-        return data
 
 
 class GithubConnection(BaseConnection):