Fix gcc 6.2 backwards compatibility

DDCore/include/DD4hep/Volumes.h

@@ -65,8 +65,11 @@ namespace dd4hep {
     class VolIDs: public std::vector<VolID> {
     public:
       typedef std::vector<VolID> Base;
-      using Base::Base;
-      /// Copy operator
+      /// Default constructor
+      VolIDs() = default;
+      /// Move constructor
+      VolIDs(VolIDs&& copy) = default;
+      /// Copy constructor
       VolIDs(const VolIDs& copy) = default;
       /// Move assignment
       VolIDs& operator=(VolIDs&& copy)  = default;

DDG4/examples/readHEPMC.py

@@ -7,7 +7,8 @@ dd4hep simulation example setup using the python configuration
 
 """
 from __future__ import absolute_import, unicode_literals
-import os, logging
+import os
+import logging
 
 logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.INFO)
 logger = logging.getLogger(__name__)