qwcode

Upgrading a package, w/o upgrading dependencies that are already satisifed

suppose the following packages: a, b, c, d

with the following dependency relationships between their versioned distributions

• a-1
• b

qwcode

option	Right align	Center align
This	This	This
column	column	column
will	will	will
be	be	be
left	right	center
aligned	aligned	aligned

qwcode

break up https://github.com/pypa/pip/pull/511

part1: MERGED https://github.com/pypa/pip/pull/548
  - system_site_packages option for reset_env
  - pypi_server.PyPIProxy.setup() occur in a sitecustomize file (not pth file) to prevent pkg_resources.working_set corruption that corrupts the sys.path

part2: MERGED https://github.com/pypa/pip/pull/553
  - migrate existing tests to new test_user_site.py module

part3: MERGED https://github.com/pypa/pip/pull/567