'Fill in the placeholders in `template_file` with the `replacements` and
write the result to `target_file`.
:param FilePath template_file: The file containing the placeholders.
:param FilePath target_file: The file to which the result will be
written.
:param dict replacements: A dictionary of variable names and
replacement values.'

def _process_template(self, template_file, target_file, replacements):

    with template_file.open() as f:
        template = f.read().decode('utf8')
    target_file.setContent(template.format(**replacements))
