For SLE 12 SP4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/systemsmanagement:saltstack:products:next:sles12-dependencies/SLE_12_SP4/systemsmanagement:saltstack:products:next:sles12-dependencies.repo
zypper refresh
zypper install python-tornado
For SLE 12 SP3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/systemsmanagement:saltstack:products:next:sles12-dependencies/SLE_12_SP3/systemsmanagement:saltstack:products:next:sles12-dependencies.repo
zypper refresh
zypper install python-tornado