regulators: Create ActionError class

Create the ActionError exception class.  This exception describes an
error that occurred while executing an action, such as i2c_write_byte.

Change-Id: Ie11b59663ba51da74967454d6ca6ad8856ddd189
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
diff --git a/phosphor-regulators/test/meson.build b/phosphor-regulators/test/meson.build
index 6db6b88..c051097 100644
--- a/phosphor-regulators/test/meson.build
+++ b/phosphor-regulators/test/meson.build
@@ -10,6 +10,7 @@
     'rule_tests.cpp',
 
     'actions/action_environment_tests.cpp',
+    'actions/action_error_tests.cpp',
     'actions/action_utils_tests.cpp',
     'actions/and_action_tests.cpp',
     'actions/if_action_tests.cpp',