The problem was mixing bytes and str values. Ensuring that everything is in bytes makes it work because urandom returns bytes.

# Encode the concatenated strings into a byte string
chars = (string.ascii_letters + string.digits + string.punctuation).encode()

char_gen = (c for c in map(urandom, repeat(1)) if c in chars)

# Use an empty byte string to join the generated bytes 
pswd_text = b''.join(islice(char_gen, None, string_len))

You can always call pswd_text.decode() to get a unicode string (str).

msg: "{{ host.items() | map('join', '=') | join(',')}}"

>>> T1 = ['13', '17', '18', '21', '32']
>>> T3 = list(map(int, T1))
>>> T3
[13, 17, 18, 21, 32]

This does the same thing as:

>>> T3 = [int(x) for x in T1]
>>> T3
[13, 17, 18, 21, 32]

so what you are doing is

>>> T3 = [[int(letter) for letter in x] for x in T1]
>>> T3
[[1, 3], [1, 7], [1, 8], [2, 1], [3, 2]]

Hope that clears up the confusion.

Using list/generator comprehensions is preferable (more Pythonic) to map():

def rot_13(string):
    alph = 'abcdefghijklmnopqrstuwxyz'
    return ''.join(alph[(alph.find(i)+13) % len(alph)] for i in string)

When you do this:

def DashInsert(str):

You're shadowing the str builtin for the scope of DashInsert, so when you try to use list_str = map(str, list_int) it won't work as expected because str is no longer Python's builtin, it's equal to the object that you've passed as str to the function. Consider renaming it, eg:

def DashInsert(text):
    list_int = map(int, list(text))
    list_str = map(str, list_int)
    return list_str