DNF  is not working on AIX 7.2 .I think its happening after aix patching.

/ /opt/freeware/bin/dnf
Traceback (most recent call last):
  File "/opt/freeware/bin/dnf", line 57, in <module>
    from dnf.cli import main
  File "/opt/freeware/lib/python3.7/site-packages/dnf/__init__.py", line 32, in <module>
    import dnf.base
  File "/opt/freeware/lib/python3.7/site-packages/dnf/base.py", line 29, in <module>
    import libdnf.transaction
  File "/opt/freeware/lib/python3.7/site-packages/libdnf/__init__.py", line 3, in <module>
    from . import common_types
  File "/opt/freeware/lib/python3.7/site-packages/libdnf/common_types.py", line 13, in <module>
    from . import _common_types
ImportError: rtld: 0712-001 Symbol lua_newuserdata was referenced
      from module /usr/opt/rpm/lib/librpmio.so(), but a runtime definition
            of the symbol was not found.

:/ #
 # lslpp -l | grep rpm.rte
  rpm.rte                4.15.1.1015  COMMITTED  RPM Package Manager
  rpm.rte                4.15.1.1015  COMMITTED  RPM Package Manager
/ #

Looks like the rpms are not updated for sometime in the machine ( dnf still uses python3.7 ? ). Please try the below commands. 

mv /usr/opt/rpm/lib/librpmio.so /usr/opt/rpm/lib/librpmio.so_orig

ar -p /usr/opt/rpm/lib/librpmio.a librpmio.so.9 > /usr/opt/rpm/lib/librpmio.so

dnf update

mv /usr/opt/rpm/lib/librpmio.so_orig /usr/opt/rpm/lib/librpmio.so