Add support for LUCI_CONTEXT.

recipe_modules/context/examples/full.py

Index: recipe_modules/context/examples/full.py
diff --git a/recipe_modules/context/examples/full.py b/recipe_modules/context/examples/full.py
index d86c89c92b32d2563ae46a5a802343dd4f980b53..557175887feac14f116026fcb3311b9942356b55 100644
--- a/recipe_modules/context/examples/full.py
+++ b/recipe_modules/context/examples/full.py
@@ -66,6 +66,15 @@ def RunSteps(api):
   with api.context(increment_nest_level=True):
     api.step('indented with wrong name', ['bash', '-c', 'echo indent?'])
 
+  # Can read initial LUCI_CONTEXT value.
+  val = api.context.luci_context['INITIAL']['k']
+  api.step('value in the context', ['echo', val])
+
+  # Can modify it.
+  with api.context(luci_context={'INITIAL': None, 'OTHER': {'k': 'zzz'}}):
+    val = api.context.luci_context['OTHER']['k']
+    api.step('value in the context', ['echo', val])
+
 
 def GenTests(api):
-  yield api.test('basic')
+  yield api.test('basic') + api.context.luci_context({'INITIAL': {'k': 'val'}})