g-s-s fails to sync images when using use_swift=false

When setting use_swift option to false, glance-simplestreams-sync fails to synchronize images due to a missing folder (/var/www/html)
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$ juju run-action --wait glance-simplestreams-sync/0 sync-images
unit-glance-simplestreams-sync-0:
  UnitId: glance-simplestreams-sync/0
  id: "113"
  results:
    Stderr: |
      /usr/lib/python2.7/dist-packages/keystoneauth1/adapter.py:179: UserWarning: Using keystoneclient sessions has been deprecated. Please update your software to use keystoneauth1.
        warnings.warn('Using keystoneclient sessions has been deprecated. '
      rsync: mkdir "/var/www/html" failed: No such file or directory (2)
      rsync error: error in file IO (code 11) at main.c(675) [Receiver=3.1.2]
    Stdout: |
      sending incremental file list
  status: completed
  timing:
    completed: 2020-10-30 10:48:52 +0000 UTC
    enqueued: 2020-10-30 10:48:46 +0000 UTC
    started: 2020-10-30 10:48:46 +0000 UTC
----

After the folder is created in the g-s-s unit, g-s-s succesfully syncs the images
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$ juju run --unit glance-simplestreams-sync/0 "mkdir -p /var/www/html"

$ juju run-action --wait glance-simplestreams-sync/0 sync-images
unit-glance-simplestreams-sync-0:
  UnitId: glance-simplestreams-sync/0
  id: "115"
  results:
    Stderr: |
      /usr/lib/python2.7/dist-packages/keystoneauth1/adapter.py:179: UserWarning: Using keystoneclient sessions has been deprecated. Please update your software to use keystoneauth1.
        warnings.warn('Using keystoneclient sessions has been deprecated. '
    Stdout: |
      sending incremental file list
      streams/
      streams/v1/
      streams/v1/auto.sync.json
      streams/v1/index.json

      sent 1,562 bytes received 66 bytes 3,256.00 bytes/sec
      total size is 4,464 speedup is 2.74
  status: completed
  timing:
    completed: 2020-10-30 10:50:55 +0000 UTC
    enqueued: 2020-10-30 10:50:49 +0000 UTC
    started: 2020-10-30 10:50:50 +0000 UTC
----