Fix gherkin-python for compiling example values with trailing backsla…

…sh (#2048)

* [gherkin] Add testdata for trailing backslash in examples

* [gherkin-python] Fix compiling for trailing backslash in examples

In case of trailing backslash in example values, backslashes in the
example values needs to be re-escaped before using regular expression
substitions of the example values in the step text.

* [gherkin] Test also internal backslash in example values

* [gherkin] Update CHANGELOG.md for the pull request #2048

gherkin/pickles/compiler.py

@@ -155,9 +155,11 @@ def _interpolate(self, name, variable_cells, value_cells):
 
         for n, variable_cell in enumerate(variable_cells):
             value_cell = value_cells[n]
+            # For the case of trailing backslash, re-escaping backslashes are needed
+            reescaped_value = re.sub(r'\\', r'\\\\', value_cell['value'])
             name = re.sub(
                 u'<{0[value]}>'.format(variable_cell),
-                value_cell['value'],
+                reescaped_value,
                 name
             )
         return name