* detect command execution status in a more robust way, fix ValueError caused during changed pipe commands when one of the command has no stdout and finishes earl.
0.5.2
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* fix seekability detection bug in pypy<2.3.0-alpha0 for wr(), ap(). (brettatoms)
0.5.1
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* fix target decoding error for ap() and wr() in py3. (brettatoms)
0.5.0
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* expand environment variables * set working directory using with statement (tburette)
0.4.0
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* add env api * add pypy support * fix: support 'utf-8' encoded string as pipe input