Create a function that allows you to convert from a positive base 10 integer to any other base from 2 to 26, and also does the reverse, converts from base 2 to 26 back to base 10. The digits in the new base will be the lower case letters a-z with a=0 and z=25. If the number is out of range for the base specified, return the error message shown in the examples.
base_conv(15, 2) ➞ "bbbb"
# 1111
base_conv(16, 2) ➞ "baaaa"
# converts 16 (base 10) to base 2
base_conv(1234, 10) ➞ "bcde"
base_conv("bac", 3) ➞ 11
# converts "bac" (base 3) to base 10
# 1*3**2 + 0*3 + 2 = 11
base_conv("dac", 3) ➞ "dac is not a base 3 number."
N/A