Description of problem:
Importing RPM with non-UTF8 chars in description fails with "pulp_rpm.plugins.importers.yum.upload:ERROR: (22882-39584) unexpected error occurred importing uploaded file: strings in documents must be valid UTF-8:" error.


Version-Release number of selected component (if applicable):
pulp-rpm-plugins-2.8.7.3-1.el7sat.noarch


How reproducible:
100%


Steps to Reproduce:
1. Have a RPM with non-UTF8 chars in %description. (to get thatm have whatever SRPM, replace %description by e.g. http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt and rpmbuild)
2. Have a custom product and a repo in it
3. Try to upload that RPM to it:

hammer -u admin -p redhat repository upload-content --organization-id=1 --id=14 --product-id=164 --path=nonUTF8.rpm 


Actual results:
Failed to upload file 'nonUTF8.rpm' to repository. Please check the file and try again.

/var/log/messages having backtrace like in https://pulp.plan.io/issues/1903


Expected results:
Upload passes


Additional info:
Simply backport https://pulp.plan.io/issues/1903 to Satellite's pulp. I have verified it works well :)