PEP 3134: Fix indentation in example. (#1699)

pep-3134.txt

@@ -171,13 +171,13 @@ The following more elaborate example demonstrates the handling of a mixture of
 
     def main(filename):
         file = open(filename)       # oops, forgot the 'w'
+        try:
             try:
-                try:
-                    compute()
-                except Exception, exc:
-                    log(file, exc)
-            finally:
-                file.clos()         # oops, misspelled 'close'
+                compute()
+            except Exception, exc:
+                log(file, exc)
+        finally:
+            file.clos()             # oops, misspelled 'close'
 
     def compute():
         1/0