PROOF-OF-CONCEPT: Adding a formatter late

RELATED TO:
* behave-contrib/behave-html-pretty-formatter#72

issue.features/issue1181.feature

@@ -0,0 +1,59 @@
+@question
+Feature: Issue #1181 -- Can I add a Formatter in the before_all() Hook
+
+  . WARNING:
+  .   * BEWARE: This is not a valid use case.
+  .   * Adding another formatter from the "environment.py" file is a hack
+  .   * You should never really need to do this.
+  .
+  . SEE ALSO:
+  .   * https://github.com/behave-contrib/behave-html-pretty-formatter/issues/72
+
+
+  Background:
+    Given a new working directory
+    And a file named "features/steps/use_behave4cmd_steps.py" with:
+      """
+      from __future__ import absolute_import
+      import behave4cmd0.passing_steps
+      """
+    And a file named "features/environment.py" with:
+      """
+      from __future__ import absolute_import, print_function
+      from behave.formatter.base import StreamOpener
+      from behave.formatter.progress import ScenarioStepProgressFormatter
+
+      def before_all(ctx):
+          stream_opener = StreamOpener("build/report4me.txt")
+          new_formatter = ScenarioStepProgressFormatter(stream_opener, ctx.config)
+          ctx._runner.formatters.append(new_formatter)
+      """
+    And a file named "features/example.feature" with:
+      """
+      Feature: Example
+        Scenario: E1 -- Ensure that all steps pass
+          Given a step passes
+          When another step passes
+          Then some step passes
+
+        Scenario: E2 -- Now every step must pass
+          When some step passes
+          Then another step passes
+      """
+
+
+  Scenario: Use new Formatter from the Environment (as POC)
+    When I run `behave -f plain features/example.feature`
+    Then it should pass with:
+      """
+      2 scenarios passed, 0 failed, 0 skipped
+      5 steps passed, 0 failed, 0 skipped, 0 undefined
+      """
+    And a file named "build/report4me.txt" should exist
+    And the file "build/report4me.txt" should contain:
+      """
+      Example    # features/example.feature
+        E1 -- Ensure that all steps pass  ...
+        E2 -- Now every step must pass  ..
+      """
+    And note that "the formatter from the environment could write its report"