[tools/version_converter] Use warnings deprecation

Author: mpsonntag

odml/tools/version_converter.py

@@ -2,9 +2,11 @@
 This module provides backwards compatibility for the VersionConverter class.
 It is deprecated and will be removed in future versions.
 """
+import warnings
 
 from .converters import VersionConverter
 
-print("[DEPRECATION WARNING] The VersionConverter file has been moved to "
-      "'odml.tools.converters' and will be removed from 'odml.tools' in future "
-      "odML releases. Please update the imports in your code accordingly.")
+_MSG = "The VersionConverter file has been moved to "\
+       "'odml.tools.converters' and will be removed from 'odml.tools' in future "\
+       "odML releases. Please update the imports in your code accordingly."
+warnings.warn(_MSG, category=DeprecationWarning, stacklevel=2)