Fix AttributeError when can not connect to Gerrit

Change-Id: I0c29bc29b9364c8203184a4dedc397e71e7ed437
Story: #2000586

git-review.1

@@ -60,7 +60,7 @@ can be
 .Ar changeNumber
 as obtained using
 .Fl \-list
-option, or it can be 
+option, or it can be
 .Ar changeNumber,patchsetNumber
 for fetching exact patchset from the change.
 In that case local branch name will have a \-patch[patchsetNumber] suffix.
@@ -353,6 +353,8 @@ Particular patchset cannot be fetched from the remote git repository.
 Specified patchset number not found in the changeset.
 .It 39
 Invalid patchsets for comparison.
+.It 40
+Connection to Gerrit was closed.
 .It 64
 Cannot checkout downloaded patchset into the new branch.
 .It 65

git_review/cmd.py

@@ -388,8 +388,9 @@ def add_remote(scheme, hostname, port, project, remote, usepushurl):
         remote_url = make_remote_url(scheme, username, hostname, port, project)
         print("Trying again with %s" % remote_url)
         if not test_remote_url(remote_url):
-            raise GitReviewException("Could not connect to gerrit at "
-                                     "%s" % remote_url)
+            raise GerritConnectionException(
+                "Could not connect to gerrit at %s" % remote_url
+            )
         asked_for_username = True
 
     if usepushurl:
@@ -1054,6 +1055,11 @@ class PatchSetNotFound(ChangeSetException):
     EXIT_CODE = 38
 
 
+class GerritConnectionException(GitReviewException):
+    """Problem to establish connection to gerrit."""
+    EXIT_CODE = 40
+
+
 class CheckoutNewBranchFailed(CommandFailed):
     "Cannot checkout to new branch"
     EXIT_CODE = 64