reposync failed with "IOError: [Errno 28] No space left on device"

Issue

• reposync failed with IOError: [Errno 28] No space left on device:

# reposync --gpgcheck -l --repoid=rhel-7-server-rpms --download_path=/var/www/html/xxx/
Loaded plugins: langpacks, product-id, subscription-manager
Traceback (most recent call last):
  File "/bin/reposync", line 343, in <module>
    main()
  File "/bin/reposync", line 175, in main
    my.doRepoSetup()
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 681, in doRepoSetup
    return self._getRepos(thisrepo, True)
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 721, in _getRepos
    self._repos.doSetup(thisrepo)
  File "/usr/lib/python2.7/site-packages/yum/repos.py", line 157, in doSetup
    self.retrieveAllMD()
  File "/usr/lib/python2.7/site-packages/yum/repos.py", line 88, in retrieveAllMD
    dl = repo._async and repo._commonLoadRepoXML(repo)
  File "/usr/lib/python2.7/site-packages/yum/yumRepo.py", line 1474, in _commonLoadRepoXML
    if self._latestRepoXML(local):
  File "/usr/lib/python2.7/site-packages/yum/yumRepo.py", line 1443, in _latestRepoXML
    oxml = self._saveOldRepoXML(local)
  File "/usr/lib/python2.7/site-packages/yum/yumRepo.py", line 1300, in _saveOldRepoXML
    shutil.copy2(local, old_local)
  File "/usr/lib64/python2.7/shutil.py", line 130, in copy2
    copyfile(src, dst)
  File "/usr/lib64/python2.7/shutil.py", line 84, in copyfile
    copyfileobj(fsrc, fdst)
IOError: [Errno 28] No space left on device