python 3.x - Problems with docker py, UnicodeDecodeError at tar read on image build -

i trying make docker image generated tar file, problem thah tar file wats generates valid, , code worked before.

t = tarfile.open('dockerfile.tar',mode='w') file_name = tarfile.tarinfo("dockerfile") file_name.size = len(dockerfile) t.addfile(file_name, bytesio(dockerfile.encode('utf-8'))) file in static_files:    t.add(static_files_path + file,arcname='root/'+file) file in files:     if type(file["data"]) == str:         file_name = tarfile.tarinfo('root/'+file["file"])         file_name.size = len(file["data"].encode())           t.addfile(file_name, bytesio(file["data"].encode()))     else:         file_name = tarfile.tarinfo('root/'+file["file"])         file_name.size = len(file["data"])         t.addfile(file_name, bytesio(file["data"]))     t.close()     docker_client = client(base_url=docker_host)     c=open('dockerfile.tar','r')     response = [line line in docker_client.build(fileobj=c, rm=false, tag=image_name, custom_context=true)] 

what get:

file "/usr/lib/python3.4/codecs.py", line 313, in decode (result, consumed) = self._buffer_decode(data, self.errors, final) unicodedecodeerror: 'utf-8' codec can't decode byte 0x89 in position 3584: invalid start byte >>> data[3580:3590] b'\x00\x00\x00\x00\x89png\r\n' 

the problem in \x89png , why hapening? bug ?

ok, problem in:

c=open('dockerfile.tar','r')   

should be

c=open('dockerfile.tar','rb')