Support usage of environment variables inside robot documentation

doc/source/robot/example.robot

@@ -11,7 +11,7 @@ ${MESSAGE}     Hello,
 *** Test Cases ***
 First Test
     [Documentation]     Thorough and relatively lengthy documentation for the example test case that
-    ...  logs ${MESSAGE} and ${NAD} and ${NAMES}.
+    ...  logs ${MESSAGE} and ${NAD} and ${NAMES}. %{RUNTIME_VAR}
     [Tags]              SWRQT-SOME_RQT  ANOTHER-TAG  SWRQT-OTHER_RQT  SYSRQT-SOME_SYSTEM_RQT
                         Log    ${MESSAGE}
                         Log    ${NAD}

mlx/robot2rst/robot_parser.py

@@ -1,3 +1,4 @@
+import os
 import re
 from collections import namedtuple
 
@@ -66,6 +67,11 @@ def visit_TestCase(self, node):
                     previous_token = token
             elif element_type == Token.TAGS:
                 tags = [el.value for el in element.tokens if el.type == Token.ARGUMENT]
+
+        for var_name in re.findall(r'%\{(.+?)\}', doc):
+            if var_name in os.environ:
+                doc = doc.replace(f'%{{{var_name}}}', os.environ[var_name])
+
         if self.evaluate_inclusion(tags):
             self.tests.append(self.TestAttributes(node.name, doc, tags))
 

tox.ini

@@ -46,8 +46,11 @@ commands =
     flake8 mlx setup.py
 
 [testenv:sphinx2.4.5]
+setenv =
+    RUNTIME_VAR = Test env variable
 deps=
     {[testenv]deps}
+    setuptools<70
     jinja2 == 2.11.3
     markupsafe == 1.1.0
     docutils == 0.17
@@ -67,6 +70,8 @@ commands=
     mlx-warnings --config warnings_config.yml --command make -C doc html
 
 [testenv:sphinx-latest]
+setenv =
+    RUNTIME_VAR = Test env variable
 deps=
     {[testenv]deps}
     sphinx