TST: add robust tests for exec_command()
TST: add robust tests for exec_command()

First, we test both stdout and stderr.

Second, we now test both _exec_command_posix() and _exec_command(), see
numpy/distutils/exec_command.py. This reveals a bug in the implementation which
will be fixed in the next commit. For now the failing test is commented out so
that all tests still pass.

empeeu/numpy,jonathanunderwood/numpy,immerrr/numpy,numpy/numpy,madphysicist/numpy,Srisai85/numpy,skwbc/numpy,NextThought/pypy-numpy,MaPePeR/numpy,mingwpy/numpy,mhvk/numpy,Srisai85/numpy,grlee77/numpy,mattip/numpy,dimasad/numpy,leifdenby/numpy,GaZ3ll3/numpy,joferkington/numpy,mwiebe/numpy,kirillzhuravlev/numpy,CMartelLML/numpy,ViralLeadership/numpy,bmorris3/numpy,ogrisel/numpy,ahaldane/numpy,empeeu/numpy,stuarteberg/numpy,nbeaver/numpy,dwillmer/numpy,dwillmer/numpy,b-carter/numpy,rgommers/numpy,yiakwy/numpy,endolith/numpy,simongibbons/numpy,BMJHayward/numpy,charris/numpy,nguyentu1602/numpy,mortada/numpy,mattip/numpy,WillieMaddox/numpy,felipebetancur/numpy,ssanderson/numpy,dato-code/numpy,moreati/numpy,skymanaditya1/numpy,leifdenby/numpy,ESSS/numpy,bmorris3/numpy,mortada/numpy,utke1/numpy,jorisvandenbossche/numpy,GrimDerp/numpy,rudimeier/numpy,ChristopherHogan/numpy,Yusa95/numpy,BabeNovelty/numpy,dato-code/numpy,bringingheavendown/numpy,Eric89GXL/numpy,rherault-insa/numpy,chatcannon/numpy,embray/numpy,MichaelAquilina/numpy,pdebuyl/numpy,trankmichael/numpy,gfyoung/numpy,b-carter/numpy,SunghanKim/numpy,hainm/numpy,hainm/numpy,WillieMaddox/numpy,endolith/numpy,SunghanKim/numpy,rgommers/numpy,simongibbons/numpy,ahaldane/numpy,Eric89GXL/numpy,skwbc/numpy,endolith/numpy,BMJHayward/numpy,Linkid/numpy,gmcastil/numpy,GrimDerp/numpy,ogrisel/numpy,has2k1/numpy,drasmuss/numpy,shoyer/numpy,AustereCuriosity/numpy,njase/numpy,BabeNovelty/numpy,andsor/numpy,dato-code/numpy,seberg/numpy,brandon-rhodes/numpy,pbrod/numpy,tacaswell/numpy,numpy/numpy,pyparallel/numpy,Dapid/numpy,anntzer/numpy,jonathanunderwood/numpy,larsmans/numpy,sigma-random/numpy,charris/numpy,dch312/numpy,githubmlai/numpy,tdsmith/numpy,cowlicks/numpy,pizzathief/numpy,embray/numpy,jankoslavic/numpy,rherault-insa/numpy,tdsmith/numpy,empeeu/numpy,jakirkham/numpy,Dapid/numpy,tdsmith/numpy,charris/numpy,dimasad/numpy,ahaldane/numpy,andsor/numpy,MSeifert04/numpy,ESSS/numpy,pbrod/numpy,naritta/numpy,Srisai85/numpy,ahaldane/numpy,grlee77/numpy,stuarteberg/numpy,ogrisel/numpy,dch312/numpy,sigma-random/numpy,KaelChen/numpy,rmcgibbo/numpy,SiccarPoint/numpy,pdebuyl/numpy,seberg/numpy,ChristopherHogan/numpy,shoyer/numpy,jonathanunderwood/numpy,AustereCuriosity/numpy,numpy/numpy,mhvk/numpy,MichaelAquilina/numpy,nbeaver/numpy,cjermain/numpy,yiakwy/numpy,dwillmer/numpy,charris/numpy,BabeNovelty/numpy,nguyentu1602/numpy,trankmichael/numpy,mattip/numpy,Linkid/numpy,Eric89GXL/numpy,GaZ3ll3/numpy,ogrisel/numpy,cjermain/numpy,bringingheavendown/numpy,mathdd/numpy,Linkid/numpy,NextThought/pypy-numpy,ssanderson/numpy,felipebetancur/numpy,chatcannon/numpy,SiccarPoint/numpy,musically-ut/numpy,argriffing/numpy,ESSS/numpy,skymanaditya1/numpy,pbrod/numpy,groutr/numpy,jakirkham/numpy,tacaswell/numpy,embray/numpy,leifdenby/numpy,jankoslavic/numpy,jschueller/numpy,skwbc/numpy,Dapid/numpy,tacaswell/numpy,mathdd/numpy,KaelChen/numpy,mwiebe/numpy,has2k1/numpy,rmcgibbo/numpy,tynn/numpy,sinhrks/numpy,mortada/numpy,jschueller/numpy,rmcgibbo/numpy,ajdawson/numpy,sonnyhu/numpy,has2k1/numpy,NextThought/pypy-numpy,brandon-rhodes/numpy,SiccarPoint/numpy,ekalosak/numpy,ahaldane/numpy,ajdawson/numpy,mattip/numpy,jakirkham/numpy,felipebetancur/numpy,GaZ3ll3/numpy,MaPePeR/numpy,immerrr/numpy,pizzathief/numpy,abalkin/numpy,utke1/numpy,cowlicks/numpy,ChristopherHogan/numpy,MSeifert04/numpy,jorisvandenbossche/numpy,ContinuumIO/numpy,ekalosak/numpy,ddasilva/numpy,trankmichael/numpy,rmcgibbo/numpy,cowlicks/numpy,sigma-random/numpy,kirillzhuravlev/numpy,githubmlai/numpy,chiffa/numpy,WillieMaddox/numpy,simongibbons/numpy,MichaelAquilina/numpy,behzadnouri/numpy,seberg/numpy,ChristopherHogan/numpy,gmcastil/numpy,githubmlai/numpy,seberg/numpy,rgommers/numpy,Yusa95/numpy,rudimeier/numpy,simongibbons/numpy,Yusa95/numpy,Srisai85/numpy,felipebetancur/numpy,jschueller/numpy,jankoslavic/numpy,mhvk/numpy,dch312/numpy,hainm/numpy,ssanderson/numpy,shoyer/numpy,maniteja123/numpy,has2k1/numpy,MSeifert04/numpy,madphysicist/numpy,andsor/numpy,pyparallel/numpy,grlee77/numpy,rherault-insa/numpy,ddasilva/numpy,jorisvandenbossche/numpy,nguyentu1602/numpy,Yusa95/numpy,yiakwy/numpy,gfyoung/numpy,CMartelLML/numpy,jakirkham/numpy,rhythmsosad/numpy,cowlicks/numpy,trankmichael/numpy,chatcannon/numpy,rajathkumarmp/numpy,sonnyhu/numpy,mingwpy/numpy,dimasad/numpy,naritta/numpy,MichaelAquilina/numpy,BMJHayward/numpy,mathdd/numpy,nbeaver/numpy,empeeu/numpy,gmcastil/numpy,anntzer/numpy,musically-ut/numpy,ChanderG/numpy,mindw/numpy,anntzer/numpy,argriffing/numpy,behzadnouri/numpy,embray/numpy,madphysicist/numpy,Eric89GXL/numpy,larsmans/numpy,GaZ3ll3/numpy,sinhrks/numpy,Anwesh43/numpy,ajdawson/numpy,dimasad/numpy,ContinuumIO/numpy,abalkin/numpy,WarrenWeckesser/numpy,musically-ut/numpy,larsmans/numpy,joferkington/numpy,jorisvandenbossche/numpy,kiwifb/numpy,jschueller/numpy,NextThought/pypy-numpy,ViralLeadership/numpy,yiakwy/numpy,GrimDerp/numpy,sonnyhu/numpy,pizzathief/numpy,shoyer/numpy,njase/numpy,ddasilva/numpy,bmorris3/numpy,mathdd/numpy,pyp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