title: Python 3 when writing json file double backslash problem
body: <p>I use <code>urllib.request</code> and <code>regex</code> for <code>html parse</code> but when I write in <code>json</code> file there is double backslash in text. How can I replace one backslash?
  I have looked at many solutions but none of them have worked.     </p>
  
  <pre><code>headers = {}
  headers['User-Agent'] = 'Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0'
  req = Request('https://www.manga-tr.com/manga-list.html', headers=headers)
  response = urlopen(req).read()
  a = re.findall(r'&lt;b&gt;&lt;a[^&gt;]* href="([^"]*)"',str(response))
  sub_req = Request('https://www.manga-tr.com/'+a[3], headers=headers)
  sub_response = urlopen(sub_req).read()
  manga = {}
  manga['manga'] = []
  manga_subject = re.findall(r'&lt;h3&gt;Tan.xc4.xb1t.xc4.xb1m&lt;.h3&gt;[^&lt;]*.n.t([^&lt;]*).t',str(sub_response))
  manga['manga'].append({'msubject': manga_subject })
  with io.open('allmanga.json', 'w', encoding='utf-8-sig') as outfile:
  outfile.write(json.dumps(manga, indent=4))
  </code></pre>
  
  <p>this is my json file</p>
  
  <pre><code>{
      "manga": [
          {
              "msubject": [
                  "  Minami Ria 16 ya\\xc5\\x9f\\xc4\\xb1ndad\\xc4\\xb1r. \\xc4\\xb0lk erkek arkada\\xc5\\x9f\\xc4\\xb1 sakatani jirou(16) ile yakla\\xc5\\x9f\\xc4\\xb1k 6 ayd\\xc4\\xb1r beraberdir. Herkes taraf\\xc4\\xb1ndan \\xc3\\xa7ifte kumru olarak g\\xc3\\xb6r\\xc3\\xbclmelerine ra\\xc4\\x9fmen ili\\xc5\\x9fkilerinde %1\\'lik bir eksiklik vard\\xc4\\xb1r. Bu eksikli\\xc4\\x9fi tamamlayabilecekler mi?"
          }
      ]
  }
  </code></pre>