* numerous improvements to the unittest module
* support for .pyc repository directories
* support for version tagged dynamic libraries
* a new futures library for concurrent programming
* a stable ABI for extension modules
* dictionary-based logging configuration
* an overhauled GIL implementation that reduces contention
* an extended email package that handles bytes messages
* a much improved ssl module with support for SSL contexts and certificate hostname matching
* a sysconfig module to access configuration information
* additions to the shutil module, among them archive file support
* many enhancements to configparser, among them mapping protocol support
* improvements to pdb, the Python debugger
* countless fixes regarding bytes/string issues; among them full support for a bytes environment (filenames, environment variables)
* many consistency and behavior fixes for numeric operations