error msg

video:webm@854x480
Traceback (most recent call last):
  File "./run.py", line 53, in <module>
    techtalk(i['pafy'])
  File "./run.py", line 40, in techtalk
    aria(audio)
  File "./run.py", line 13, in aria
    subprocess.call(args)
  File "/usr/lib/python3.4/subprocess.py", line 537, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/lib/python3.4/subprocess.py", line 859, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.4/subprocess.py", line 1395, in _execute_child
    restore_signals, start_new_session, preexec_fn)
UnicodeEncodeError: 'ascii' codec can't encode character '\u2014' in position 45: ordinal not in range(128)

yt.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-

import pafy
import os
import subprocess
import logging
logging.getLogger().setLevel(logging.ERROR)


def aria(stream):
    args = ['aria2c', '-o',stream.filename, stream.url]
    subprocess.call(args)

def convaudio(file):
    conv_args = ['ffmpeg', '-i', file, '-c:a', 'libfdk_aac', '-p:a', 
                'aac_he_v2', '-b:a', '24k', file[0:-4]+'-done.m4a']
    subprocess.call(conv_args) 
    os.remove(file)
    os.rename(file[0:-4]+'-done.m4a', file)

def getvideo(videostreams):
    #print(videostreams)
    l = [ "video:webm@854x480", "video:m4v@854x480", "video:webm@640x480",
        "video:m4v@640x360", "video:webm@320x240"]
    for i in l:
        for vid in videostreams:
            if vid.__str__() == i:
                print(vid)
                return vid

def getyt(url):
    return pafy.new(url)


def techtalk(yt):
    audio = yt.audiostreams.pop()
    video = getvideo(yt.videostreams)
    # print("====================="+video.__str__())
    aria(audio)
    convaudio(audio.filename)
    aria(video)
    conv_args = ['ffmpeg', '-i', video.filename, '-i', audio.filename, '-c:a',
                 'copy', '-c:v', 'copy', audio.filename[0:-4]+'.'+'mkv']
    if subprocess.call(conv_args) == 0:
        os.remove(video.filename)
        os.remove(audio.filename)

url ="PLKprbVwttd70Euv8zJIJRBdGurLRG9-5d"

pl = pafy.get_playlist(url)
for i in pl['items']:
    techtalk(i['pafy'])