Colt will not repair a cracked barrel.
Python barrels cannot be "drilled out, replaced/bonded".
The factory method is to junk the barrel, since cracks are usually the result of shooting hot reloads, especially reloads using a slower burning powder.
The loads carburize and crack the thinner forcing cone, since the thin cone area can't dissipate the excess heat fast enough.
In short, the barrel has been structurally weakened, and shortening the barrel doesn't "Fix" the problem, even when the barrel is set back.
Some gunsmiths will ATTEMPT to "save" the barrel by setting the barrel back, and removing the cracked area.
This is done by lathe cutting the barrel shoulder forward, cutting off the threaded portion to remove the cracked area, re-threading the shank to restore the threading, then cutting a new forcing cone.
This is in effect, setting the barrel back however much is needed to remove the cracked portion.
Unfortunately, the structural weakening and "metal fatigue" is NOT removed, unless you're planning on converting a 6" inch barrel into a 4" inch barrel.
There are "gunsmith's" who will do setbacks on damaged barrels, but these barrels will almost always quickly develop cracks again, and you run a high risk of damage to the frame.
Bottom, line is, a cracked barrel has been fatally damaged, and there is no practical repair.
Having someone attempt to "fix" it will be money wasted.
Simply call Colt, and ask the tech rep if they will repair a Python barrel with a cracked forcing cone.
Unless something has REALLY changed at Colt, they'll say no.