That error flashes 3 times and then it aborts that process, not decompiling Minecraft at all. I've checked just about everything I can think of: Java and Python versions, presence or absence of every file listed in the MCP readme, the MCP readme itself, running the .sh as a superuser, opening the .sh in a text editor and running the component commands as a superuser...
I really just don't have any idea what's going on here. Can someone more familiar with MCP help me out with this?
Unless that's somehow different from doing "sudo bash decompile.sh" then it's been done.
EDIT: Apparently, in spite of ostensibly having read and write permissions for everything in the download, there was something else blocking me from opening the files in the MCP folder through terminal. Using chmod fixed it.