cmdrewrite: rename variable and move it closer to where it is used
Renaming to satisfy pep8-naming linter plugin, which complained on this
variable because all-uppercase names are reserved for constants, and constants
need to be module-level. This variable is not a good choice for moving up to
the module level because it's used only in one place.
Additionally, let's have it closer to the place it's actually used to
potentially avoid an extra call to _() function (however cheap it may be).