The get/pop CA method cause exception if looked for component is missing

Functionality added by this MR is related to new/CA JO. The CAs can be queried for components (i.e. public tools). Typically when no object is found this means a mistake (typo in the name for instance). With this change, such a mistake would result in an exception being raised. This is the default behaviour. In cases when it is actually possible that the component is missing additional option can be provided: acceptAbsent. Then client code can check if the returned value is None and act accordingly.

Tagging @wlampl @mhodgkin @emoyse @goetz @fwinkl @rbielski PS> Launching all unit tests to catch possible mistakes in all areas.

Control/AthenaConfiguration/python/ComponentAccumulator.py

@@ -344,6 +344,8 @@ class ComponentAccumulator(object):
         The CA will not keep any reference to the AlgTool.
         """
         tool=self._privateTools
+        if tool is None:
+            raise ConfigurationError("Private tool(s) requested, but none are present")
         self._privateTools=None
         return tool
 
@@ -441,6 +443,9 @@ class ComponentAccumulator(object):
         hits=[a for a in self._conditionsAlgs if a.name==name]
         if (len(hits)>1):
             raise ConfigurationError("More than one conditions algorithm with name {} found".format(name))
+        if (len(hits)==0):
+            raise ConfigurationError("No conditions algorithm with name {} found".format(name))
+
         return hits[0]
 
     def addService(self,newSvc,primary=False,create=False):
@@ -517,7 +522,8 @@ class ComponentAccumulator(object):
     def __getOne(self, allcomps, name=None, typename="???"):
         selcomps = allcomps if name is None else [ t for t in allcomps if t.name == name ]
         if len( selcomps ) == 0:
-            return None
+            raise ConfigurationError(f"Requested component of name {name} but is missing" )
+
         if len( selcomps ) == 1:
             return selcomps[0]
         raise ConfigurationError("Number of {} available {} which is != 1 expected by this API".format(typename, len(selcomps)) )