215075ae30
Fix build with Python < 2.7.
File "./glsl/ir_expression_operation.py", line 360, in get_enum_name
return "ir_{}op_{}".format(("un", "bin", "tri", "quad")[self.num_operands-1], self.name)
ValueError: zero length field name in format
Fixes: e31c72a331 ("glsl: Convert tuple into a class")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>