Implement different workaround for https://bugs.python.org/issue27777 suggested by jsm/Joseph Myers. Subclass cgi.FieldStorage into BinaryFieldStorage and use that class rather then monkey patching cgi.FieldStorage.make_file. This should eliminate race conditions issues inherent with the prior way I tried to do it by flipping the class method back and forth at runtime. Also import new class into rest_common.py and use it in place of old mechanism.