[cleanup] Upgrade syntax

Using https://github.com/asottile/pyupgrade

1. `__future__` imports and `coding: utf-8` were removed
2. Files were rewritten with `pyupgrade --py36-plus --keep-percent-format`
3. f-strings were cherry-picked from `pyupgrade --py36-plus`

Extractors are left untouched (except removing header) to avoid unnecessary merge conflicts

1 files changed, 2 insertions, 6 deletions

diff --git a/devscripts/make_readme.py b/devscripts/make_readme.py
index 3f56af744..5d85bcc63 100755
--- a/devscripts/make_readme.py
+++ b/devscripts/make_readme.py
@@ -2,10 +2,6 @@
 
 # yt-dlp --help | make_readme.py
 # This must be run in a console of correct width
-
-from __future__ import unicode_literals
-
-import io
 import sys
 import re
 
@@ -15,7 +11,7 @@ helptext = sys.stdin.read()
 if isinstance(helptext, bytes):
     helptext = helptext.decode('utf-8')
 
-with io.open(README_FILE, encoding='utf-8') as f:
+with open(README_FILE, encoding='utf-8') as f:
     oldreadme = f.read()
 
 header = oldreadme[:oldreadme.index('## General Options:')]
@@ -25,7 +21,7 @@ options = helptext[helptext.index('  General Options:'):]
 options = re.sub(r'(?m)^  (\w.+)$', r'## \1', options)
 options = options + '\n'
 
-with io.open(README_FILE, 'w', encoding='utf-8') as f:
+with open(README_FILE, 'w', encoding='utf-8') as f:
     f.write(header)
     f.write(options)
     f.write(footer)