README.md in trackler-2.2.1.75

- old
+ new

@@ -1,6 +1,6 @@
-# Pascals Triangle
+# Pascal's Triangle
 
 Compute Pascal's triangle up to a given number of rows.
 
 In Pascal's Triangle each number is computed by adding the numbers to
 the right and left of the current position in the previous row.
@@ -11,9 +11,24 @@
   1 2 1
  1 3 3 1
 1 4 6 4 1
 # ... etc
 ```
+
+## Exception messages
+
+Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to
+indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not
+every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include
+a message.
+
+To raise a message with an exception, just write it as an argument to the exception type. For example, instead of
+`raise Exception`, you shold write:
+
+```python
+raise Exception("Meaningful message indicating the source of the error")
+```
+
 
 ## Submitting Exercises
 
 Note that, when trying to submit an exercise, make sure the solution is in the `exercism/python/<exerciseName>` directory.
 