Fix bugs I found in this app

[chitly]

Thank you a lot, for improving this app.
After I use this repo, I found 3 bugs, then I fix them and want to share them with your repo.

1. After I migrate existing files, I found some files I manually remove, so I add the code to check the file exists on disk.

if not s3_file_regex_match(file['file_url']) and is_file_exists(file['name']):
    upload_existing_files_s3(file['name'], file['file_name'])
    return True

def is_file_exists(file_name):
    if frappe.db.exists('File', {'name': file_name}):
        doc = frappe.get_doc('File', file_name)
        return doc.exists_on_disk()
    return False

2. When I uploaded the file to AWS S3, then I have an error about file_name in my language, then I fix it.

import urllib
encoded_file_name = urllib.parse.quote(file_name)
params['ResponseContentDisposition'] = 'filename={}'.format(encoded_file_name)

3. Finally, I uploaded the file in my doc, but the URL didn't change, then I found this PR, and it work to fix this problem.

frappe.db.sql("""UPDATE `tabFile` SET file_url=%s, folder=%s,
    old_parent=%s, content_hash=%s WHERE name=%s""", (
    file_url, 'Home/Attachments', 'Home/Attachments', key, doc.name))

doc.reload()

[Namekkural]

I would love to see these fixes implemented in to the parent branch. For now I'm using you repo @chitly

[pythonpen]

Thanks for the contributions @chitly- will merge them soon ;)