avocado.core.exceptions: Avoid avocado crashing on unknown error status

Since someone might want to be funny and raise those
exceptions, it is safer to make them to return "FAIL"
instead of "NEVER_RAISE_THIS", so avocado does not
crash.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/core/exceptions.py

@@ -21,8 +21,11 @@ class JobBaseException(Exception):
 
     """
     The parent of all job exceptions.
+
+    You should be never raising this, but just in case, we'll set its
+    status' as FAIL.
     """
-    status = "NEVER_RAISE_THIS"
+    status = "FAIL"
 
 
 class JobError(Exception):
@@ -37,8 +40,11 @@ class TestBaseException(Exception):
 
     """
     The parent of all test exceptions.
+
+    You should be never raising this, but just in case, we'll set its
+    status' as FAIL.
     """
-    status = "NEVER_RAISE_THIS"
+    status = "FAIL"
 
 
 class TestSetupFail(TestBaseException):