[platform] improve testing assertions

recipe_modules/platform/test_api.py

Index: recipe_modules/platform/test_api.py
diff --git a/recipe_modules/platform/test_api.py b/recipe_modules/platform/test_api.py
index 934b0bbf552b323736185b618d68def25806c3f5..ef2cd082ded4ce28f1282d9dd3136d3f870adc36 100644
--- a/recipe_modules/platform/test_api.py
+++ b/recipe_modules/platform/test_api.py
@@ -8,20 +8,20 @@ class PlatformTestApi(recipe_test_api.RecipeTestApi):
   @recipe_test_api.mod_test_data
   @staticmethod
   def name(name):
-    assert name in ('win', 'linux', 'mac')
+    assert name in ('win', 'linux', 'mac'), 'unknown platform %r' % (name,)
     return name
 
   @recipe_test_api.mod_test_data
   @staticmethod
   def bits(bits):
-    assert bits in (32, 64)
+    assert bits in (32, 64), 'unknown bitness %r' % (bits,)
     return bits
 
   @recipe_test_api.mod_test_data
   @staticmethod
   def cpu_count(cpu_count):
-    assert isinstance(cpu_count, int)
-    assert cpu_count > 0
+    assert isinstance(cpu_count, int), 'bad type %r' % (type(cpu_count),)
+    assert cpu_count > 0, 'bad cpu_count %r' % (cpu_count,)
     return cpu_count
 
   def __call__(self, name, bits):