You may get this error once in a while when pushing the changes on your git branch. This is an uncommon issue and below are the domain of reasons due to which you might get this error:
Case: when pushing local branch
If your branch is a local branch, the most likely reason is that a remote branch already exists with the same name on the repository. Try changing the name of your local branch and then try gain push your commits.
Command to rename the branch:
git branch -m <new_name>
Case: when pushing commits in remote branch
If yours is not a local branch, the most likely reason is that your local code is not merged with the target remote branch. Try merging the local code with the target branch and then push the commits.
Commands to merge local branch with remote branch:
git merge <target branch>
git merge remote/login