Trying to display script's output to the webui makes for messy output

I've got this function in my page file that runs a python script using the built-in `StartCommand.php` from the webui:
 

function scan(cmd,title,plg,func,start=0,button=0) {
  // start  = 0 : run command only when not already running (default)
  // start  = 1 : run command unconditionally
  // button = 0 : show CLOSE button (default)
  // button = 1 : hide CLOSE button
  $('#scan-button').prop('disabled', true);
  $('#scanDir').prop('disabled', true);
  $('#dbDir').prop('disabled', true);
  nchan_plugins.start();
  $.post('/webGui/include/StartCommand.php',{cmd:cmd+' nchan',start:start},function(pid) {
    if (pid==0) {
      nchan_plugins.stop();
      $('div.spinner.fixed').hide();
      $(".sweet-alert").addClass('alert');
      return;
    }
    swal({title:title,text:"<pre id='swaltext'></pre><hr>",html:true,animation:'none',showConfirmButton:button==0,confirmButtonText:"<?=_('Close')?>"},function(close){
      nchan_plugins.stop();
      $('div.spinner.fixed').hide();
      $('.sweet-alert').hide('fast');
      setTimeout(function(){bannerAlert("<?=_('Attention - scanning continues in background')?> ["+pid.toString().padStart(8,'0')+"]<i class='fa fa-bomb fa-fw abortOps' title=\"<?=_('Abort background process')?>\" onclick='abortScan("+pid+")'></i>",cmd,plg,func,start);});
    });
    $('button.confirm').prop('disabled',button!=0);
  });
}

When I run the python script in the terminal during development, everything looks great.
https://github.com/bobbintb/UnRAID-DeDuper/blob/release/src/scripts/main.py
But when I test it in UnRAID in the webui, there are all kinds of character encoding issues. I don't really know how to deal with that in the webui side of things as I'm still kind of new at web development. Instead of the neatly displayed progress bars (2), I get something like this:
 

0%|�[34m �[0m| (30.4G
0%|�[34m �[0m| 0.00/11.9G�[
1%|�[34m▍ �[0m| 122M/11.9G�[A 0%|�[34m▏ �[0m|, 0/116 (30.4G
2%|�[34m▉ �[0m| 244M/11.9G�[A 1%|�[34m▍ �[0m|, 0/116 (30.4G
3%|�[34m█▍ �[0m| 366M/11.9G�[A 1%|�[34m▋ �[0m|, 0/116 (30.4G
4%|�[34m█▉ �[0m| 488M/11.9G�[A 2%|�[34m▊ �[0m|, 0/116 (30.4G
5%|�[34m██▍ �[0m| 609M/11.9G�[A 2%|�[34m█ �[0m|, 0/116 (30.4G
6%|�[34m██▉ �[0m| 731M/11.9G�[A 3%|�[34m█▎ �[0m|, 0/116 (30.4G
7%|�[34m███▍ �[0m| 853M/11.9G�[A 3%|�[34m█▍ �[0m|, 0/116 (30.4G
8%|�[34m███▉ �[0m| 975M/11.9G�[A 3%|�[34m█▋ �[0m|, 0/116 (30.4G
9%|�[34m████▍ �[0m| 1.07G/11.9G�[A 4%|�[34m█▉ �[0m|, 0/116 (30.4G
10%|�[34m████▉ �[0m| 1.19G/11.9G�[A 4%|�[34m██ �[0m|, 0/116 (30.4G
11%|�[34m█████▍ �[0m| 1.31G/11.9G�[A 5%|�[34m██▎ �[0m|, 0/116 (30.4G
12%|�[34m█████▉ �[0m| 1.43G/11.9G�[A 5%|�[34m██▌ �[0m|, 0/116 (30.4G
13%|�[34m██████▍ �[0m| 1.55G/11.9G�[A 5%|�[34m██▋ �[0m|, 0/116 (30.4G
14%|�[34m██████▉ �[0m| 1.67G/11.9G�[A 6%|�[34m██▉ �[0m|, 0/116 (30.4G
15%|�[34m███████▍ �[0m| 1.79G/11.9G�[A 6%|�[34m███▏ �[0m|, 0/116 (30.4G
16%|�[34m███████▉ �[0m| 1.90G/11.9G�[A 7%|�[34m███▎ �[0m|, 0/116 (30.4G
17%|�[34m████████▍ �[0m| 2.02G/11.9G�[A 7%|�[34m███▌ �[0m|, 0/116 (30.4G
18%|�[34m████████▉ �[0m| 2.14G/11.9G�[A 8%|�[34m███▊ �[0m|, 0/116 (30.4G
19%|�[34m█████████▍ �[0m| 2.26G/11.9G�[A 8%|�[34m███▉ �[0m|, 0/116 (30.4G
20%|�[34m█████████▉ �[0m| 2.38G/11.9G�[A 8%|�[34m████▏ �[0m|, 0/116 (30.4G
21%|�[34m██████████▍ �[0m| 2.50G/11.9G�[A 9%|�[34m████▍ �[0m|, 0/116 (30.4G
22%|�[34m██████████▉ �[0m| 2.62G/11.9G�[A 9%|�[34m████▋ �[0m|, 0/116 (30.4G
23%|�[34m███████████▍ �[0m| 2.74G/11.9G�[A 10%|�[34m████▊ �[0m|, 0/116 (30.4G
24%|�[34m███████████▉ �[0m| 2.86G/11.9G�[A 10%|�[34m█████ �[0m|, 0/116 (30.4G
25%|�[34m████████████▍ �[0m| 2.98G/11.9G�[A 11%|�[34m█████▎ �[0m|, 0/116 (30.4G
26%|�[34m████████████▉ �[0m| 3.09G/11.9G�[A 11%|�[34m█████▍ �[0m|, 0/116 (30.4G

It looks like this normally:
 

  5%|██▌                                               |, 0/116 (30.4G)
 12%|█████▉                                            | 1.43G/11.9G

I'm sure it has to do with the ANSI characters or something and I know it's probably just a simple thing for someone who knows what they are doing to just specify the correct encoding. Even after spending a few hours on it, I just don't know where to begin looking. Any Ideas?