Tweaked repo adding

ee/core/apt_repo.py

@@ -17,6 +17,7 @@ class EERepo():
             repo_file_path = ("/etc/apt/sources.list.d/"
                               + EEVariables().ee_repo_file)
             try:
+                if repo_url not in open(repo_file_path).read():
                     with open(repo_file_path, "a") as repofile:
                         repofile.write(repo_url)
                         repofile.close()