With:
!python3
 -*- coding: utf-8 -*-

import glob
import re

for f in glob.glob('contribs/**/*.scss', recursive=True):
    with open(f, encoding='utf-8') as s:
        text = s.read()

    def calc(value):
        number = float(value.group(1)) / 10.0
        number = int(number) if number == int(number) else number
        return str(number) + 'rem'

    text = re.sub(r'\b([\.0-9]+)px\b', calc, text)

    with open(f, 'w', encoding='utf-8') as s:
        s.write(text)

With:

!python3
 -*- coding: utf-8 -*-

import glob
import re

for f in glob.glob('contribs/**/*.scss', recursive=True):
    with open(f, encoding='utf-8') as s:
        text = s.read()

    def calc(value):
        number = float(value.group(1)) / 1.6
        number = str(int(number)) if number == int(number) else "{:.2f}".format(number)
        return number + 'rem'

    text = re.sub(r'\b([\.0-9]+)rem\b', calc, text)

    with open(f, 'w', encoding='utf-8') as s:
        s.write(text)