store status code in UaStatusCodeError

This allows the user to handle some status codes differently
from others.

opcua/common/uaerrors.py

@@ -2,14 +2,38 @@
 Define exceptions to be raised at various places in the stack
 """
 
-
 class UaError(RuntimeError):
     pass
 
 
 class UaStatusCodeError(UaError):
-    pass
+    """
+    This exception is raised when a bad status code is encountered.
+
+    It exposes the status code number in the `code' property, so the
+    user can distinguish between the different status codes and maybe
+    handle some of them.
+
+    The list of status error codes can be found in opcua.ua.status_codes.
+    """
+    def __init__(self, code):
+        """
+        :param code: The code of the exception. (Should be a number.)
+        """
+        UaError.__init__(self, code)
+
+    def __str__(self):
+        # import here to avoid circular import problems
+        import opcua.ua.status_codes as status_codes
+
+        return "{1}({0})".format(*status_codes.get_name_and_doc(self.code))
 
+    @property
+    def code(self):
+        """
+        The code of the status error.
+        """
+        return self.args[0]
 
 class UaStringParsingError(UaError):
     pass

opcua/ua/uatypes.py

@@ -450,11 +450,12 @@ class StatusCode(FrozenClass):
 
     def check(self):
         """
-        raise en exception if status code is anything else than 0
-        use is is_good() method if not exception is desired
+        Raises an exception if the status code is anything else than 0 (good).
+
+        Use the is_good() method if you do not want an exception.
         """
         if self.value != 0:
-            raise UaStatusCodeError("{}({})".format(self.doc, self.name))
+            raise UaStatusCodeError(self.value)
 
     def is_good(self):
         """