Description of problem:
spacecmd softwarechannel_clonetree aborts part way through the tree with error:

ERROR: redstone.xmlrpc.XmlRpcFault: unhandled internal exception: ERROR: duplicate key value violates unique constraint "rhn_ce_ce_uq"
  Detail: Key (channel_id, errata_id)=(1731, 25865) already exists.

Here, channel_id=1731 is the channel in the process of being cloned, and I suspect this is done inside a transaction which is rolled back after this error is encountered since there is no channel with that ID visible through the webui).
errata_id refers to a cloned errata, present in two children (fedora-26-updates and fedora26-updates-testing) of the base channel. In this case, the channel tree being cloned is already a clone of the "head" tree, i.e. head-fedora -(already cloned to)-> 201801-fedora -(being cloned to)-> qa-fedora.

Version-Release number of selected component (if applicable):
spacecmd-2.7.16-1.el7.noarch
spacewalk-backend-server-2.7.139-1.el7.noarch

How reproducible:
Every time this base channel is cloned


Steps to Reproduce:
1. spacecmd softwarechannel_clonetree -s '201801-fedora' -x '/^201801-/qa-/' --gpg-copy
2. 
3.

Actual results:
Child channels that are before the failing channel are cloned. The failing channel and subsequent channels are not cloned. The above error is printed

Expected results:
The full tree of channels should be cloned without error

Additional info: