feat(problem-03.py): completed problem.

lab-02/problem-03.py

@@ -1 +1,16 @@
-# Write a Python program that opens a file and handles a FileNotFoundError exception if the file does not exist.
+# Write a Python program that opens a file and handles a FileNotFoundError exception if the file does not exist.
+
+# Define open_file function to open files specified by user
+def open_file(filename):
+    # Try to open entered filename
+    try:
+        open(filename)
+    except FileNotFoundError:
+        # Handle expected FileNotFoundError and print error message
+        print('That file cannot be found.')
+    except PermissionError:
+        # Handle PermissionError exception for file existing in directory used in problem-05.py
+        print('Insufficient permission to open file')
+
+#Prompt user to enter a file name to be opened
+open_file(filename = input('Enter the name of the file to open: '))