Description of problem:

Fedora/RISC-V (riscv64) kernel does not have /proc/self/loginuid thus misc.getloginuid() returns None and then the conversion to int fails. This happens while running appliance-creator to create nightly disk images.

https://github.com/rpm-software-management/dnf/blob/58197bd1207525fd28cc135f88c2b988357daf5d/dnf/db/history.py#L448

[..]
RPMDB altered outside of DNF.
['/']
Traceback (most recent call last):
  File "/usr/bin/appliance-creator", line 173, in <module>
    sys.exit(main())
  File "/usr/bin/appliance-creator", line 151, in main
    creator.install()
  File "/usr/lib/python2.7/site-packages/imgcreate/creator.py", line 726, in install
    dbo.runInstall()
  File "/usr/lib/python2.7/site-packages/imgcreate/dnfinst.py", line 211, in runInstall
    ret = self.do_transaction(TransactionProgress())
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 904, in do_transaction
    self._run_transaction(cb=cb)
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 974, in _run_transaction
    tid = self.history.beg(rpmdbv, using_pkgs, [], cmdline)
  File "/usr/lib/python2.7/site-packages/dnf/db/history.py", line 448, in beg
    int(misc.getloginuid())
TypeError: int() argument must be a string or a number, not 'NoneType'
Unmounting directory /var/tmp/imgcreate-eGs3tj/install_root/
Removing compat symlinks
Unmapping /dev/loop0
Losetup remove /dev/loop0
[..]

Version-Release number of selected component (if applicable):

We moved to DNF 3.0.2 and this started to happen. This particular code was added ~5 months ago and landed in DNF 3.

How reproducible:

Boot in Fedora/RISC-V QEMU, e.g.: https://fedorapeople.org/groups/risc-v/disk-images/

[root@hifive ~]# cat /proc/self/loginuid
cat: /proc/self/loginuid: No such file or directory

[root@hifive ~]# python
Python 2.7.15 (default, May  7 2018, 14:37:14) 
[GCC 8.1.1 20180502 (Red Hat 8.1.1-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from dnf.yum import misc
>>> a = misc.getloginuid()
>>> type(a)
<type 'NoneType'>
>>> print(a)
None