could you please provide version of rhn-setup and rhn-client tools are you using? (rpm -q)
I've saw this bug before but I'd definitely say we've already fixed that.

(In reply to Tomáš Kašpárek from comment #1)
> could you please provide version of rhn-setup and rhn-client tools are you
> using? (rpm -q)
> I've saw this bug before but I'd definitely say we've already fixed that.

I'm using these versions :

rhn-setup-2.3.16-1.el7.noarch
rhn-client-tools-2.3.16-1.el7.noarch

Any idea with these infos ?

I've tried to replay te scenario fro a new kickstated machine with the same result, really no idea to solve this bug ?
Thx by advance

Same problem here with fresh installation on Fedora22 :

[root@test01 ~]# rhnreg_ks
Traceback (most recent call last):
  File "/usr/sbin/rhnreg_ks", line 25, in <module>
    from rhn.connections import idn_puny_to_unicode
ImportError: cannot import name idn_puny_to_unicode



[root@test01 ~]# rpm -qa | grep -i rhn
rhn-setup-2.4.5-1.fc22.noarch
rhn-check-2.4.5-1.fc22.noarch
rhnlib-2.5.72-1.fc22.noarch
rhn-client-tools-2.4.5-1.fc22.noarch
rhnsd-5.0.14-3.fc22.x86_64
yum-rhn-plugin-2.2.7-1.fc22.noarch
rhn-org-trusted-ssl-cert-1.0-1.noarch

I just got started using centos and spacewalk and ran into the same error when registering my first client in centos 7.

When I looked at "/usr/lib/python2.7/site-packages/rhn/connections.py" I noticed the definitions where named "idn_pune_to_unicode" and "idn_ascii_to_pune" instead of "idn_puny_to_unicode" and "idn_ascii_to_puny" as rhnreg_ks was looking for. Changing the names fixed the issue.

I can confirm that the fix in comment 5 "fixes" the issue on Fedora 22 using the in distro packages - the external repo (yum.spacewalkproject.org) doesn't have F22 packages.

I just tried to register a RHEL7 server to a Spacewalk machine with:
* client packages from RHEL7:
 rhn-setup-2.0.2-6.el7.noarch
 rhn-client-tools-2.0.2-6.el7.noarch
* client packages from spacewalk 2.3 client repo:
 rhn-setup-2.3.16-1.el7.noarch
 rhn-client-tools-2.3.16-1.el7.noarch

I experienced no issues.

I was also able to register a fedora22 machine to a Spacewalk server with:
* client packages from spacewalk nightly client repo:
 rhn-setup-2.4.6-1.fc22.noarch
 rhn-client-tools-2.4.6-1.fc22.noarch

Registration with client packages from Fedora22:
 rhn-setup-2.4.5-1.fc22.noarch
 rhn-client-tools-2.4.5-1.fc22.noarch
FAILED with:
Traceback (most recent call last):
  File "/usr/sbin/rhnreg_ks", line 25, in <module>
    from rhn.connections import idn_puny_to_unicode
ImportError: cannot import name idn_puny_to_unicode
To get this fixed, please open a BZ for Fedora - rhn-client-tools component, as the issue was most probably fixed in upstream, but not in fedora yet.

As I do not see any misbehavior in Spacewalk (client) packages, I'm closing this bug as NEXTRELEASE (as Spacewalk client packages for fedora22 were not part of any Spacewalk release yet, only available in nightly repo). Feel free to re-open, in case I overlooked something. Thank you.

> Registration with client packages from Fedora22:
>  rhn-setup-2.4.5-1.fc22.noarch
>  rhn-client-tools-2.4.5-1.fc22.noarch
> FAILED with:
> Traceback (most recent call last):
>   File "/usr/sbin/rhnreg_ks", line 25, in <module>
>     from rhn.connections import idn_puny_to_unicode
> ImportError: cannot import name idn_puny_to_unicode
> To get this fixed, please open a BZ for Fedora - rhn-client-tools component,
> as the issue was most probably fixed in upstream, but not in fedora yet.

There is already Bug 1235574 opened, that should address the issue in Fedora22.

This BZ closed some time during 2.5, 2.6 or 2.7.  Adding to 2.7 tracking bug.