Check project existence for push too, and

we don't have to check for deploy key for downloading
because deploy key could certainly download when it
could already read the project.

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7383#note_19578626

lib/gitlab/git_access.rb

@@ -9,8 +9,6 @@ module Gitlab
       download: 'You are not allowed to download code from this project.',
       deploy_key_upload:
         'This deploy key does not have write access to this project.',
-      deploy_key:
-        'This deploy key does not have access to this project.',
       no_repo: 'A repository for this project does not exist yet.'
     }
 
@@ -33,10 +31,11 @@ module Gitlab
       check_active_user! unless deploy_key?
       check_project_accessibility!
       check_command_existence!(cmd)
+      check_repository_existence!
 
       case cmd
       when *DOWNLOAD_COMMANDS
-        download_access_check
+        download_access_check unless deploy_key?
       when *PUSH_COMMANDS
         push_access_check(changes)
       end
@@ -47,20 +46,12 @@ module Gitlab
     end
 
     def download_access_check
-      passed = if deploy_key
-                 deploy_key.has_access_to?(project)
-               elsif user
-                 user_can_download_code? || build_can_download_code?
-               end || guest_can_download_code?
+      passed = user_can_download_code? ||
+               build_can_download_code? ||
+               guest_can_download_code?
 
       unless passed
-        message = if deploy_key
-                    ERROR_MESSAGES[:deploy_key]
-                  else
-                    ERROR_MESSAGES[:download]
-                  end
-
-        raise UnauthorizedError, message
+        raise UnauthorizedError, ERROR_MESSAGES[:download]
       end
     end
 
@@ -75,7 +66,6 @@ module Gitlab
 
       return if changes.blank? # Allow access.
 
-      check_repository_existence!
       check_change_access!(changes)
     end