Python Format Multiline String not working

Question

So I'm trying to generate html files for each day of the year while changing day, month in my template. I've tried the follwing but I get the following error:

Traceback (most recent call last):
  File "c:\Users\Galax\Dokumente\Programming\Python\GenerateBirthdayCounters\main.py", line 23, in <module>
    make_file(str(month),str(day))
  File "c:\Users\Galax\Dokumente\Programming\Python\GenerateBirthdayCounters\main.py", line 9, in make_file
    f.write(html.format(day=day.rjust(2, "0"),month=month.rjust(2, "0"),bg="#660066"))
KeyError: '\n  --smaller'

This is my main code:

import os
from html import html

os.mkdir("pages")
os.chdir("pages")

def make_file(month, day):
    with open(f"{day}.html", "w") as f:
        f.write(html.format(day=day.rjust(2, "0"),month=month.rjust(2, "0"),bg="#660066"))

for month in range(1,13):
    os.mkdir(str(month))
    os.chdir(str(month))
    
    if month == 2:
        for day in range(1,29):
            make_file(str(month),str(day))
    elif month % 2 == 0:
        for day in range(1,32):
            make_file(str(month),str(day))
    else:
        for day in range(1,31):
            make_file(str(month),str(day))
    
    os.chdir("..")

And this is html.py simplified:

html = """
some text
othertext {month} jsd
text {day} anytest
blabla {bg}
"""

complete file see here (if necessary): https://pastebin.com/pX089Cwc