proper python exception handling

examples/parallel/davinci/pwordfreq.py

@@ -19,7 +19,7 b' from __future__ import division'
 
 try : #python2
     from urllib import urlretrieve
-except : #python3
+except ImportError: #python3
     from urllib.request import urlretrieve
 
 davinci_url = "http://www.gutenberg.org/cache/epub/5000/pg5000.txt"
@@ -78,7 +78,7 b" if __name__ == '__main__':"
     
     try : #python2
         cwd = os.path.abspath(os.getcwdu())
-    except : #python3
+    except AttributeError: #python3
         cwd = os.path.abspath(os.getcwd())
     fnames = [ os.path.join(cwd, 'davinci%i.txt'%i) for i in range(n)]
     tic = time.time()

examples/parallel/pi/pidigits.py

@@ -23,7 +23,7 b' from matplotlib import pyplot as plt'
 
 try : #python2
     from urllib import urlretrieve
-except : #python3
+except ImportError : #python3
     from urllib.request import urlretrieve
 
 	# Top-level functions