SCons release 2.5.1 now available from the download page at SourceForge. This release should be used instead of 2.5.0. This release fixes several issues. This will be the last release to support Python versions earlier than 2.7, as we begin to move toward supporting Python 3. You can view ChangeLog
Note that due to improvements in cross language scanning 2.5.1 may find a non-trivial amount of previously undiscovered dependancies which may cause rebuilds and longer runtimes.