utils, examples: Add ExperimentManager CM

Adds an ExperimentManager context manager for scripts:

 - No more ugly stack traces after execution if something goes wrong

 - No more ugly and easy to forget try-finally blocks

1 files changed, 2 insertions, 3 deletions

diff --git a/examples/example.py b/examples/example.py
index 11e8331..9f0ce03 100755
--- a/examples/example.py
+++ b/examples/example.py
@@ -3,6 +3,7 @@
 # An example script using the rumba package
 
 from rumba.model import *
+from rumba.utils import ExperimentManager
 
 # import testbed plugins
 import rumba.testbeds.emulab as emulab
@@ -44,12 +45,10 @@ exp = rl.Experiment(tb, nodes = [a, b])
 
 print(exp)
 
-try:
+with ExperimentManager(exp):
     exp.swap_in()
     exp.bootstrap_prototype()
     c1 = Client("rinaperf", options ="-t perf -s 1000 -c 10000")
     s1 = Server("rinaperf", arrival_rate=2, mean_duration=5, options = "-l", nodes = [a], clients = [c1])
     sb = StoryBoard(exp, duration=3600, servers = [s1])
     sb.start()
-finally:
-    exp.swap_out()