Issue #506: Provides example how problem can be avoided.

issue.features/issue0506.feature

@@ -0,0 +1,77 @@
+@issue
+@user_error
+@python2.problem
+Feature: Issue #506 -- Behave stops on error
+
+    . ANALYSIS:
+    .   Using exception.__cause__ = original_exception causes problems in Python2
+    .   When you use the Python3 chained-exception mechanism,
+    .   you should better ensure that the "original_exception.__traceback__" attribute
+    .   exists. Otherwise, a new exception (missing attribute) is raised
+    .   when you format the traceback,
+
+    Scenario:
+      Given a new working directory
+      And a file named "features/steps/pass_steps.py" with:
+        """
+        from behave import step
+
+        @step('{word:w} step passes')
+        def step_passes(context, word):
+            pass
+
+        """
+      And a file named "features/steps/steps.py" with:
+        """
+        from behave import when, then
+        from behave._types import ChainedExceptionUtil
+        import copy
+
+        @when('I bad chained-exception causes my step to fail')
+        def step_bad_usage_of_chained_exception(context):
+            # -- BAD IMPLEMENATION:
+            exception = ZeroDivisionError('integer division or modulo by zero')
+            exception.__cause__ = copy.copy(exception)
+            raise exception
+
+        @when('a chained-exception causes my step to fail')
+        def step_chained_exception_causes_failure(context):
+            try:
+                raise ZeroDivisionError("OOPS-1")
+            except ZeroDivisionError as e:
+                e2 = RuntimeError("OOPS-2")
+                ChainedExceptionUtil.set_cause(e2, e)
+                raise e2
+
+        @then('this step must be executed')
+        def step_check_step(context):
+            pass
+        """
+      And a file named "features/syndrome.feature" with:
+        """
+        Feature: Failing step which can lead to stop behave
+
+          @failing
+          Scenario: Run stopping behave scenario
+            When a chained-exception causes my step to fail
+            Then this step must be executed
+        """
+      When I run "behave -f plain features/syndrome.feature"
+      Then it should fail with:
+        """
+        0 scenarios passed, 1 failed, 0 skipped
+        """
+      And the command output should contain:
+        """
+          ZeroDivisionError: OOPS-1
+
+        The above exception was the direct cause of the following exception:
+
+        Traceback (most recent call last):
+        """
+      And the command output should contain:
+        """
+          File "features/steps/steps.py", line 19, in step_chained_exception_causes_failure
+            raise e2
+        RuntimeError: OOPS-2
+        """