[KVM-AUTOTEST PATCH 1/7] [RFC] Fix Unhandled* exceptions

[Michael Goldish <mgoldish@redhat.com>]

In recent Python version, when exceptions are unpickled their __init__() method
is called again.  The parameters passed to __init__() upon unpickling are
*self.args.  Because the first execution of __init__() sets self.args to
something different from the parameters passed to __init__() (by passing
something to Exception.__init__()), upon unpickling __init__() is called with
unexpected parameters.

For example, if a NameError is raised in a test, UnhandledTestFail.__init__()
will call
Exception.__init__(self, "Unhandled NameError: ...").
Upon unpickling, UnhandledTestFail.__init__() will be called with "Unhandled
NameError: ..." which is a string.  It will then call
Exception.__init__(self, "Unhandled str: Unhandled NameError: ...")
because str is not an instance of TestFail.  The resulting exception's __str__()
method will return "Unhandled str: Unhandled NameError: ..." which isn't pretty.

To fix this, this patch makes the Unhandled* exceptions rely on __str__()
and attributes (self.unhandled_exception and self.traceback) instead of
__init__() and self.args.  An alternative solution could be to check whether
the parameter passed to __init__() is a string, and if so, pass it to the parent
exception's __init__() without modification.

Signed-off-by: Michael Goldish <mgoldish@redhat.com>
---
 client/bin/job.py          |    6 ++--
 client/common_lib/error.py |   51 ++++++++++++++++++++++++++++---------------
 2 files changed, 36 insertions(+), 21 deletions(-)

diff --git a/client/bin/job.py b/client/bin/job.py
index 3d552ce..f4306fc 100644
--- a/client/bin/job.py
+++ b/client/bin/job.py
@@ -1182,13 +1182,13 @@ def runjob(control, drop_caches, options):
         sys.exit(1)
 
     except error.JobError, instance:
-        logging.error("JOB ERROR: " + instance.args[0])
+        logging.error("JOB ERROR: " + str(instance))
         if myjob:
             command = None
             if len(instance.args) > 1:
                 command = instance.args[1]
-                myjob.record('ABORT', None, command, instance.args[0])
-            myjob.record('END ABORT', None, None, instance.args[0])
+                myjob.record('ABORT', None, command, str(instance))
+            myjob.record('END ABORT', None, None, str(instance))
             assert myjob._record_indent == 0
             myjob.complete(1)
         else:
diff --git a/client/common_lib/error.py b/client/common_lib/error.py
index 42dfe2b..71ba4e5 100644
--- a/client/common_lib/error.py
+++ b/client/common_lib/error.py
@@ -44,14 +44,19 @@ class JobError(AutotestError):
 class UnhandledJobError(JobError):
     """Indicates an unhandled error in a job."""
     def __init__(self, unhandled_exception):
-        if isinstance(unhandled_exception, JobError):
-            JobError.__init__(self, *unhandled_exception.args)
+        JobError.__init__(self, unhandled_exception)
+        self.unhandled_exception = unhandled_exception
+        self.traceback = traceback.format_exc()
+
+    def __str__(self):
+        if isinstance(self.unhandled_exception, JobError):
+            return JobError.__str__(self.unhandled_exception)
         else:
             msg = "Unhandled %s: %s"
-            msg %= (unhandled_exception.__class__.__name__,
-                    unhandled_exception)
-            msg += "\n" + traceback.format_exc()
-            JobError.__init__(self, msg)
+            msg %= (self.unhandled_exception.__class__.__name__,
+                    self.unhandled_exception)
+            msg += "\n" + self.traceback
+            return msg
 
 
 class TestBaseException(AutotestError):
@@ -85,27 +90,37 @@ class TestWarn(TestBaseException):
 class UnhandledTestError(TestError):
     """Indicates an unhandled error in a test."""
     def __init__(self, unhandled_exception):
-        if isinstance(unhandled_exception, TestError):
-            TestError.__init__(self, *unhandled_exception.args)
+        TestError.__init__(self, unhandled_exception)
+        self.unhandled_exception = unhandled_exception
+        self.traceback = traceback.format_exc()
+
+    def __str__(self):
+        if isinstance(self.unhandled_exception, TestError):
+            return TestError.__str__(self.unhandled_exception)
         else:
             msg = "Unhandled %s: %s"
-            msg %= (unhandled_exception.__class__.__name__,
-                    unhandled_exception)
-            msg += "\n" + traceback.format_exc()
-            TestError.__init__(self, msg)
+            msg %= (self.unhandled_exception.__class__.__name__,
+                    self.unhandled_exception)
+            msg += "\n" + self.traceback
+            return msg
 
 
 class UnhandledTestFail(TestFail):
     """Indicates an unhandled fail in a test."""
     def __init__(self, unhandled_exception):
-        if isinstance(unhandled_exception, TestFail):
-            TestFail.__init__(self, *unhandled_exception.args)
+        TestFail.__init__(self, unhandled_exception)
+        self.unhandled_exception = unhandled_exception
+        self.traceback = traceback.format_exc()
+
+    def __str__(self):
+        if isinstance(self.unhandled_exception, TestFail):
+            return TestFail.__str__(self.unhandled_exception)
         else:
             msg = "Unhandled %s: %s"
-            msg %= (unhandled_exception.__class__.__name__,
-                    unhandled_exception)
-            msg += "\n" + traceback.format_exc()
-            TestFail.__init__(self, msg)
+            msg %= (self.unhandled_exception.__class__.__name__,
+                    self.unhandled_exception)
+            msg += "\n" + self.traceback
+            return msg
 
 
 class CmdError(TestError):
-- 
1.7.3.4