I wrongly minutes. Here is actual data of execution speeds.  There is
magnitude of difference (almost 130x faster). Measured on  macbook pro
with 2 cores and 4 Gig mem.

Before Patch:

$ ./python.exe -m timeit -s "import urllib.parse; x='a%20' * 100000"
"urllib.parse.unquote(x)"
10 loops, best of 3: 26.8 sec per loop

After Patch:

$ ./python.exe -m timeit -s "import urllib.parse; x='a%20' * 100000"
"urllib.parse.unquote(x)"
10 loops, best of 3: 205 msec per loop