email to lowercase

validity_check.py

@@ -18,6 +18,7 @@ if __name__ == "__main__":
         print('You broke file format by suppressing/adding "," !\n')
         exit(1)
 
+    author = author.lower()
     if author not in curr_line[0] and (author not in prev_line[0]) :
         print("You modify the line of another student or use a different email than the one written !\n")
         exit(1)