Did you see: 
https://listserv.fnal.gov/scripts/wa.exe?A2=ind1611&L=SCIENTIFIC-LINUX-ERRATA&F=&S=&P=1819 
?

On 11/22/2016 02:06 PM, Devin A. Bougie wrote:
> Hi, All.  It appears that httpd24-libnghttp2 is missing from SL6.  This prevents yum updates on systems that have httpd24-httpd or any httpd24 modules installed.
>
> For example:
> ------
> yum update httpd24-httpd
> Loaded plugins: priorities, security
> Setting up Update Process
> ...
> --> Finished Dependency Resolution
> Error: Package: httpd24-httpd-2.4.18-11.sl6.x86_64 (softwarecollections)
>             Requires: libnghttp2-httpd24.so.14()(64bit)
>   You could try using --skip-broken to work around the problem
>   You could try running: rpm -Va --nofiles --nodigest
> ------
>
> And in particular:
> ------
> ================================================================================
> Package Arch Version Repository Size
> ================================================================================
> Removing:
> httpd24-httpd x86_64 2.4.12-4.sl6.2 @softwarecollections/6.6 3.6 M
> Removing for dependencies:
> httpd24-httpd-devel x86_64 2.4.12-4.sl6.2 @softwarecollections/6.6 770 k
> perl516-mod_perl x86_64 2.0.8-5.20130221svn1448242.el6
> @softwarecollections/6.5 6.0 M
> perl516-mod_perl-devel x86_64 2.0.8-5.20130221svn1448242.el6
> @softwarecollections/6.5 917 k
> python27-mod_wsgi x86_64 3.4-12.el6 @softwarecollections/6.5 199 k
> python33-mod_wsgi x86_64 3.4-14.el6 @softwarecollections/6.5 203 k
> ruby193-mod_passenger40 x86_64 4.0.18-11.el6 @softwarecollections/6.5 566 k
>
> Transaction Summary
> ================================================================================
> Remove 7 Package(s)
> ------
>
> For what it's worth, it is available from the centos repo at:
> http://mirror.centos.org/centos/6/sclo/x86_64/rh/httpd24/httpd24-libnghttp2-1.7.1-1.el6.x86_64.rpm
>
> Many thanks,
> Devin