Add dependency info for mysql-postgresql converter
Add dependency info for mysql-postgresql converter

Running converter with Python 2.6.x installed gives the following error:
AttributeError: 'module' object has no attribute 'check_output'

After installing Python 2.7.x everything works fine.
Kambda/Mobbr,ferdinandrosario/gitlabhq,kitech/gitlabhq,liyakun/gitlabhq,hacsoc/gitlabhq,ibiart/gitlabhq,mrb/gitlabhq,duduribeiro/gitlabhq,LytayTOUCH/gitlabhq,salipro4ever/gitlabhq,yfaizal/gitlabhq,dplarson/gitlabhq,sekcheong/gitlabhq,rfeese/gitlab-ce,NuLL3rr0r/gitlabhq,fantasywind/gitlabhq,michaKFromParis/sparkslab,fantasywind/gitlabhq,tk23/gitlabhq,martijnvermaat/gitlabhq,theodi/gitlabhq,kemenaran/gitlabhq,yonglehou/gitlabhq,copystudy/gitlabhq,LytayTOUCH/gitlabhq,vjustov/gitlabhq,8thcolor/testing-public-gitlabhq,dreampet/gitlab,chadyred/gitlabhq,allistera/gitlabhq,cui-liqiang/gitlab-ce,since2014/gitlabhq,jrjang/gitlab-ce,childbamboo/gitlabhq,louahola/gitlabhq,stellamiranda/mobbr-gitlabhq,ZeoAlliance/gitlabhq,Exeia/gitlabhq,Tyrael/gitlabhq,t-zuehlsdorff/gitlabhq,mavimo/gitlabhq,123Haynes/gitlabhq,bozaro/gitlabhq,123Haynes/gitlabhq,Datacom/gitlabhq,Devin001/gitlabhq,yuyue2013/ss,DanielZhangQingLong/gitlabhq,darkrasid/gitlabhq,joalmeid/gitlabhq,bigsurge/gitlabhq,OtkurBiz/gitlabhq,kemenaran/gitlabhq,folpindo/gitlabhq,kitech/gitlabhq,OtkurBiz/gitlabhq,sideci-sample/sideci-sample-gitlabhq,williamherry/gitlabhq,allistera/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,aaronsnyder/gitlabhq,mathstuf/gitlabhq,fgbreel/gitlabhq,yuyue2013/ss,NKMR6194/gitlabhq,julianengel/gitlabhq,allysonbarros/gitlabhq,flashbuckets/gitlabhq,MauriceMohlek/gitlabhq,NARKOZ/gitlabhq,ttasanen/gitlabhq,phinfonet/mobbr-gitlabhq,nmav/gitlabhq,SVArago/gitlabhq,pulkit21/gitlabhq,bozaro/gitlabhq,mathstuf/gitlabhq,mmkassem/gitlabhq,sideci-sample/sideci-sample-gitlabhq,yama07/gitlabhq,Soullivaneuh/gitlabhq,mmkassem/gitlabhq,Telekom-PD/gitlabhq,chenrui2014/gitlabhq,julianengel/gitlabhq,rumpelsepp/gitlabhq,WSDC-NITWarangal/gitlabhq,yulchitaj/TEST3,jrjang/gitlab-ce,gorgee/gitlabhq,mmkassem/gitlabhq,yatish27/gitlabhq,cinderblock/gitlabhq,hzy001/gitlabhq,chadyred/gitlabhq,salipro4ever/gitlabhq,jirutka/gitlabhq,OtkurBiz/gitlabhq,fscherwi/gitlabhq,fpgentil/gitlabhq,koreamic/gitlabhq,rebecamendez/gitlabhq,stoplightio/gitlabhq,rumpelsepp/gitlabhq,dvrylc/gitlabhq,youprofit/gitlabhq,adaiguoguo/gitlab_globalserarch,ikappas/gitlabhq,sonalkr132/gitlabhq,Razer6/gitlabhq,fantasywind/gitlabhq,screenpages/gitlabhq,wangcan2014/gitlabhq,fgbreel/gitlabhq,ordiychen/gitlabhq,sue445/gitlabhq,fendoudeqingchunhh/gitlabhq,rfeese/gitlab-ce,iiet/iiet-git,cncodog/gitlab,ksoichiro/gitlabhq,dplarson/gitlabhq,johnmyqin/gitlabhq,Razer6/gitlabhq,revaret/gitlabhq,louahola/gitlabhq,stellamiranda/mobbr-gitlabhq,szechyjs/gitlabhq,Datacom/gitlabhq,theodi/gitlabhq,wangcan2014/gitlabhq,jrjang/gitlabhq,sue445/gitlabhq,koreamic/gitlabhq,ayufan/gitlabhq,lvfeng1130/gitlabhq,dwrensha/gitlabhq,bozaro/gitlabhq,hzy001/gitlabhq,yonglehou/gitlabhq,icedwater/gitlabhq,kemenaran/gitlabhq,johnmyqin/gitlabhq,LUMC/gitlabhq,tempbottle/gitlabhq,duduribeiro/gitlabhq,szechyjs/gitlabhq,delkyd/gitlabhq,t-zuehlsdorff/gitlabhq,luzhongyang/gitlabhq,OlegGirko/gitlab-ce,youprofit/gitlabhq,larryli/gitlabhq,gorgee/gitlabhq,sekcheong/gitlabhq,hq804116393/gitlabhq,joalmeid/gitlabhq,rfeese/gitlab-ce,chenrui2014/gitlabhq,iiet/iiet-git,yatish27/gitlabhq,Exeia/gitlabhq,bigsurge/gitlabhq,rumpelsepp/gitlabhq,ordiychen/gitlabhq,jvanbaarsen/gitlabhq,ibiart/gitlabhq,Kambda/mobbr-gitlabhq,martinma4/gitlabhq,joalmeid/gitlabhq,martinma4/gitlabhq,dukex/gitlabhq,zBMNForks/gitlabhq,k4zzk/gitlabhq,rebecamendez/gitlabhq,daiyu/gitlab-zh,mathstuf/gitlabhq,axilleas/gitlabhq,eliasp/gitlabhq,daiyu/gitlab-zh,bigsurge/gitlabhq,dplarson/gitlabhq,rebecamendez/gitlabhq,Datacom/gitlabhq,chadyred/gitlabhq,LUMC/gitlabhq,childbamboo/gitlabhq,shinexiao/gitlabhq,yonglehou/gitlabhq,tim-hoff/gitlabhq,delkyd/gitlabhq,H3Chief/gitlabhq,MauriceMohlek/gitlabhq,stanhu/gitlabhq,initiummedia/gitlabhq,LUMC/gitlabhq,ferdinandrosario/gitlabhq,daiyu/gitlab-zh,mavimo/gitlabhq,LytayTOUCH/gitlabhq,michaKFromParis/gitlabhq,fpgentil/gitlabhq,bbodenmiller/gitlabhq,openwide-java/gitlabhq,NARKOZ/gitlabhq,martijnvermaat/gitlabhq,WSDC-NITWarangal/gitlabhq,ikappas/gitlabhq,pulkit21/gitlabhq,SVArago/gitlabhq,yatish27/gitlabhq,louahola/gitlabhq,yfaizal/gitlabhq,bozaro/gitlabhq,salipro4ever/gitlabhq,Razer6/gitlabhq,mr-dxdy/gitlabhq,OtkurBiz/gitlabhq,k4zzk/gitlabhq,mrb/gitlabhq,adaiguoguo/gitlab_globalserarch,H3Chief/gitlabhq,8thcolor/testing-public-gitlabhq,pjknkda/gitlabhq,axilleas/gitlabhq,Tyrael/gitlabhq,OlegGirko/gitlab-ce,MauriceMohlek/gitlabhq,k4zzk/gitlabhq,pulkit21/gitlabhq,sakishum/gitlabhq,martijnvermaat/gitlabhq,since2014/gitlabhq,Kambda/mobbr-gitlabhq,bbodenmiller/gitlabhq,cui-liqiang/gitlab-ce,hzy001/gitlabhq,zBMNForks/gitlabhq,mmkassem/gitlabhq,johnmyqin/gitlabhq,darkrasid/gitlabhq,H3Chief/gitlabhq,cncodog/gitlab,revaret/gitlabhq,openwide-java/gitlabhq,gorgee/gitlabhq,manfer/gitlabhq,michaKFromParis/gitlabhq,jrjang/gitlabhq,flashbuckets/gitlabhq,icedwater/gitlabhq,gopeter/gitlabhq,since2014/gitlabhq,vjustov/gitlabhq,MauriceMohlek/gitlabhq,zrbsprite/gitlabhq,windymid/test2,cinderblock/gitlabhq,folpindo/gitlabhq,adaiguoguo/gitlab_globalserarch,jaepyoung/gitlabhq,NARKOZ/gi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