Perusal, Synthesis, Bliss

June 24, 2017: assertion when using rdiff-backup to backup a directory on an external hard drive

The error obtained is
  File "/usr/lib/python2.7/dist-packages/rdiff_backup/", line 233, in set_regress_inc
    assert len(newer_incs) <= 1, "Too many recent increments"
AssertionError: Too many recent increments
It is difficult to find a solution on the web. See in particular here. I do not want to remove my backup and start a new one (almost 1 To to backup and many files: it is about one night long!), but I do not care in previous increment backups, only the previous one is enough. The solution is thus to do:
$ rdiff-backup --remove-older-than 1s BACKUP_DIRECTORY
where BACKUP_DIRECTORY is the rdiff-backup directory root on the external hard drive. After that the assertion "Too many recent increments" disappears.