Print a letter diamond based on the input character

This program takes in a character (alphabetic) and creates a diamond starting with 'A' and containing the given character as the widest point of the diamond. If the input is lowercase, it will automatically be turned to uppercase. If the input is not alphabetic, or it has more than one character, the program will inform the user and exit.

This can be run on the command line using the following syntax: python3 letter_diamond.py [character]

Examples of tests can be found in files test1, test2 and test3