Remove bez

[JeanChristopheMorinPerso]

The bez build system has been deprecated and almost completely removed. We should remove it completely in 3.0.

rez/src/rez/build_system.py

Lines 81 to 109 in 371644d

	# Special case - bez. This is an old deprecated build system,
	# which expects a rezbuild.py file. Include info in error showing
	# how to port to a custom build command.
	#
	if os.path.exists(os.path.join(working_dir, "rezbuild.py")):
	msg = (
	"No build system is associated with the path %s.\n"
	"\n"
	"There is a rezbuild.py file present, suggesting you were "
	"using the deprecated bez build system. You need to use a "
	"custom build command instead. You can port your existing "
	"rezbuild.py like so:\n"
	"\n"
	"Add this line to package.py:\n"
	"\n"
	" build_command = 'python {root}/rezbuild.py {install}'\n"
	"\n"
	"Add these lines to rezbuild.py:\n"
	"\n"
	" if __name__ == '__main__':\n"
	" import os, sys\n"
	" build(\n"
	" source_path=os.environ['REZ_BUILD_SOURCE_PATH'],\n"
	" build_path=os.environ['REZ_BUILD_PATH'],\n"
	" install_path=os.environ['REZ_BUILD_INSTALL_PATH'],\n"
	" targets=sys.argv[1:]\n"
	" )"
	)
	raise BuildSystemError(msg % working_dir)