Fix for web2py upload widget that was missing 'for' attr in label

web2py_upload_single_widget.py

class Upload(FormWidget):

    DEFAULT_WIDTH = '150px'
    ID_DELETE_SUFFIX = '__delete'
    GENERIC_DESCRIPTION = 'file'
    DELETE_FILE = 'delete'

    @staticmethod
    def widget(field, value, download_url=None, **attributes):
        """
        generates a INPUT file tag.

        Optionally provides an A link to the file, including a checkbox so
        the file can be deleted.
        All is wrapped in a DIV.

        see also: :meth:`FormWidget.widget`

        :param download_url: Optional URL to link to the file (default = None)
        """

        default=dict(
            _type='file',
            )
        attr = Upload._attributes(field, default, **attributes)

        inp = INPUT(**attr)

        if download_url and value:
            if callable(download_url): 
                url = download_url(value)
            else:
                url = download_url + '/' + value
            (br, image) = ('', '')
            if Upload.is_image(value):
                br = BR()
                image = IMG(_src = url, _width = Upload.DEFAULT_WIDTH)

            requires = attr["requires"]
            if requires == [] or isinstance(requires, IS_EMPTY_OR):
                inp = DIV(inp, BR(),
                          INPUT(_type='checkbox',
                                _name=field.name + Upload.ID_DELETE_SUFFIX,
                                _id=field.name + Upload.ID_DELETE_SUFFIX),
                          LABEL(Upload.DELETE_FILE,_for=field.name + Upload.ID_DELETE_SUFFIX),
                           br, image)
            else:
                inp = DIV(inp, '[',
                          A(Upload.GENERIC_DESCRIPTION, _href = url),
                          ']', br, image)
        return inp

    @staticmethod
    def represent(field, value, download_url=None):
        """
        how to represent the file:

        - with download url and if it is an image: <A href=...><IMG ...></A>
        - otherwise with download url: <A href=...>file</A>
        - otherwise: file

        :param field: the field
        :param value: the field value
        :param download_url: url for the file download (default = None)
        """

        inp = UploadWidget.GENERIC_DESCRIPTION

        if download_url and value:
            if callable(download_url):
                url = download_url(value)
            else:
                url = download_url + '/' + value
            if UploadWidget.is_image(value):
                inp = IMG(_src = url, _width = UploadWidget.DEFAULT_WIDTH)
            inp = A(inp, _href = url)

        return inp

    @staticmethod
    def is_image(value):
        """
        Tries to check if the filename provided references to an image

        Checking is based on filename extension. Currently recognized:
           gif, png, jp(e)g, bmp

        :param value: filename
        """

        extension = value.split('.')[-1].lower()
        if extension in ['gif', 'png', 'jpg', 'jpeg', 'bmp']:
            return True
        return False