def _encode_invalid_chars(component, allowed_chars, encoding="utf-8"):
    """Percent-encodes a URI component without reapplying
    onto an already percent-encoded component.
    """
    if component is None:
        return component

    component = six.ensure_text(component)

    # Normalize existing percent-encoded bytes.
    # Try to see if the component we're encoding is already percent-encoded
    # so we can skip all '%' characters but still encode all others.
    component, percent_encodings = PERCENT_RE.subn(
        lambda match: match.group(0).upper(), component
    )

    uri_bytes = component.encode("utf-8", "surrogatepass")
    is_percent_encoded = percent_encodings == uri_bytes.count(b"%")
    encoded_component = bytearray()

    for i in range(0, len(uri_bytes)):
        # Will return a single character bytestring on both Python 2 & 3
        byte = uri_bytes[i : i + 1]
        byte_ord = ord(byte)
        if (is_percent_encoded and byte == b"%") or (
            byte_ord < 128 and byte.decode() in allowed_chars
        ):
            encoded_component += byte
            continue
        encoded_component.extend(b"%" + (hex(byte_ord)[2:].encode().zfill(2).upper()))

    return encoded_component.decode(encoding)
Percent-encodes a URI component without reapplying
    onto an already percent-encoded component.
    
product/gradle-plugin/src/main/python/pip/_vendor/urllib3/util/url.py