This article explains the 'sysctl: 'none' not '!none'' error seen during MX device upgrades.

user@Re0> request system software add /var/tmp/junos-vmhost-install-mx-x86-64-19.4R3-S7.3.tgz no-validate

Verified junos-vmhost-install-mx-x86-64-19.4R3-S7.3 signed by PackageProductionEc_2019 method ECDSA256+SHA256
ERROR: junos-vmhost-install-mx-x86-64-19.4R3-S7.3: sysctl: 'none' not '!none'
ERROR: package junos-vmhost-install-mx-x86-64-19.4R3-S7.3 fails requirements
ERROR: Failed to add junos-vmhost-install-mx-x86-64-19.4R3-S7.3.tgz

Please verify the routing-engine hardware model with the below command:

user@Re0> show chassis hardware | match Routing

Routing Engine 0 REV 09  xxxxxxxxxxx  xxxxxxxxxxx    RE-S-1800x4
Routing Engine 1 REV 09  xxxxxxxxxxx  xxxxxxxxxxx    RE-S-1800x4

As the RE-S-1800x4 is a hardware-based Routing Engine, it cannot utilize a VM-host image. The current image verification failure is a direct result of this incompatibility. Please download the correct image. 

If you need further help, please open a case with JTAC Support.