Dead easy.
from xor import xor_solver
# Initialise the solver with the set of characters used to write the plaintext.
x = xor_solver(string.printable)
# Run to spit out a list of (key, plaintext) pairs.
solutions = x.solve(
"fd3cebb2e009e5a0f537c6bcef38ef85ee24f8bcff14e5b9eb38e3bbe6", #Your ciphertext
4, #Your key length
is_hex=True #Flag to interpret hex digits as hex.
)
#Show key-value pairs
print solutions
assert("flag{YoungLithePutridDolphin}" in [s[1] for s in solutions])