Fix error formatting in debug mode

Backtrace filtering was only disabled for exception cause, this change
ensure no backtrace filtering at all in debug mode.

* Prevent main exception filtering when debug mode is enabled;
* Test when exception cause must be displayed;
* Test how exception cause must be displayed.

features/cli/debug.feature

@@ -1,11 +1,13 @@
 Feature: CLI debug option
 
-  Background:
-    Given a recipe with:
-      """
-      task(:trigger_error) { fail 'some error' }
-      """
-
-  Scenario: reports recipe errors
+  Scenario: reports recipe errors with their cause
+    Given a recipe with an error
     When I execute the recipe with option -d
     Then the output must match /\ARuntimeError:.*\n\ncause:\nRuntimeError:/
+
+  Scenario: does not exclude anything from backtrace
+    Given a recipe using a remote
+    When I execute the recipe on unknown remote target with option -d
+    Then the output must contain "producer-core"
+    And the output must contain "net-ssh"
+    And the output must contain ruby lib directory

features/steps/output_steps.rb

@@ -26,6 +26,10 @@ Then /^the error output must contain exactly "([^"]+)"$/ do |content|
   assert_exact_output content, all_stderr
 end
 
+Then /^the output must contain ruby lib directory$/ do
+  assert_partial_output RbConfig::CONFIG['rubylibdir'], all_output
+end
+
 Then /^the output must not contain ruby lib directory$/ do
   assert_no_partial_output RbConfig::CONFIG['rubylibdir'], all_output
 end

features/steps/recipe_steps.rb

@@ -27,6 +27,11 @@ When /^I execute the recipe on unknown remote target$/ do
   assert_matching_output '\ASocketError', all_output
 end
 
+When /^I execute the recipe on unknown remote target with option (-.+)$/ do |option|
+  run_simple "producer recipe.rb #{option} -t #unknown_host.test", false
+  assert_matching_output '\ASocketError', all_output
+end
+
 When /^I successfully execute the recipe$/ do
   step 'I execute the recipe'
   assert_exit_status 0