There is chance that in your copyright text there is unicode characters not properly encoded try use the codecs module
import re
import shutil
import os
import codecs
copyrightloc = 'C:/DATA/pyscripts/copyright.txt'
rootdir = 'C:/DATA/pyscripts/02_CODE'
dstdir = 'C:/DATA/pyscripts/codecopy'
spielfile = codecs.open(copyrightloc, "r", encoding="utf8")
spiel = spielfile.read()
for subdir, dirs, files in os.walk(rootdir):
for file in files:
if file.endswith(".cs"):
with codecs.open(subdir+'/'+file, "r+",encoding="utf8") as codefile , open(dstdir+'/'+file, 'w') as destfile:
destfile.write(spiel+'\n' + codefile.read())