• The maximum thread count can now be set at import-time by setting the
  environment variable 'NUMEXPR_MAX_THREADS'. The default number of
  max threads was lowered from 4096 (which was deemed excessive) to 64.
• A number of imports were removed (pkg_resources) or made lazy (cpuinfo) in
  order to speed load-times for downstream packages (such as pandas, sympy,
  and tables). Import time has dropped from about 330 ms to 90 ms. Thanks to
  Jason Sachs for pointing out the source of the slow-down.
• Thanks to Alvaro Lopez Ortega for updates to benchmarks to be compatible with
  Python 3.
• Travis and AppVeyor now fail if the test module fails or errors.
• Thanks to Mahdi Ben Jelloul for a patch that removed a bug where constants
  in where calls would raise a ValueError.
• Fixed a bug whereby all-constant power operations would lead to infinite
  recursion.