Closes google#36338

Update validations.py python script.
Fixed the behavior of validate-user function in validations.py

Fixes google#36338

Course3/Lab4/validations.py

@@ -15,10 +15,22 @@ def validate_user(username, minlen):
     # Usernames can only use letters, numbers, dots and underscores
     if not re.match('^[a-z0-9._]*$', username):
         return False
+    # Username can only start with a letter
+    if re.match('^[0-9._]', username):
+        return False
     # Usernames can't begin with a number
     if username[0].isnumeric():
         return False
     return True
 
 
+print(validate_user("blue.kale", 3)) # True
+
+print(validate_user(".blue.kale", 3)) # Currently True, should be False
+
+print(validate_user("red_quinoa", 4)) # True
+
+print(validate_user("_red_quinoa", 4)) # Currently True, should be False
+
+