test: add tx modfication helper function in feature_cltv.py
test: add tx modfication helper function in feature_cltv.py

+ reformat python imports
+ fix PEP8 warnings (all except E501 line too long)

mruddy/bitcoin,tecnovert/particl-core,yenliangl/bitcoin,tecnovert/particl-core,apoelstra/bitcoin,pataquets/namecoin-core,GroestlCoin/bitcoin,fujicoin/fujicoin,Xekyo/bitcoin,instagibbs/bitcoin,particl/particl-core,JeremyRubin/bitcoin,bitcoin/bitcoin,instagibbs/bitcoin,yenliangl/bitcoin,jlopp/statoshi,mm-s/bitcoin,AkioNak/bitcoin,namecoin/namecoin-core,instagibbs/bitcoin,AkioNak/bitcoin,jambolo/bitcoin,namecoin/namecore,namecoin/namecore,pataquets/namecoin-core,kallewoof/bitcoin,yenliangl/bitcoin,achow101/bitcoin,tecnovert/particl-core,prusnak/bitcoin,bitcoinknots/bitcoin,anditto/bitcoin,fujicoin/fujicoin,namecoin/namecore,kallewoof/bitcoin,lateminer/bitcoin,jlopp/statoshi,domob1812/bitcoin,mm-s/bitcoin,yenliangl/bitcoin,mruddy/bitcoin,jambolo/bitcoin,achow101/bitcoin,mruddy/bitcoin,sipsorcery/bitcoin,MarcoFalke/bitcoin,mruddy/bitcoin,jamesob/bitcoin,dscotese/bitcoin,jamesob/bitcoin,andreaskern/bitcoin,domob1812/bitcoin,ajtowns/bitcoin,kallewoof/bitcoin,mm-s/bitcoin,dscotese/bitcoin,lateminer/bitcoin,prusnak/bitcoin,JeremyRubin/bitcoin,lateminer/bitcoin,MarcoFalke/bitcoin,AkioNak/bitcoin,sipsorcery/bitcoin,bitcoinsSG/bitcoin,pataquets/namecoin-core,fanquake/bitcoin,anditto/bitcoin,jlopp/statoshi,instagibbs/bitcoin,apoelstra/bitcoin,instagibbs/bitcoin,prusnak/bitcoin,ajtowns/bitcoin,rnicoll/bitcoin,fujicoin/fujicoin,sstone/bitcoin,bitcoinknots/bitcoin,bitcoinsSG/bitcoin,namecoin/namecore,ElementsProject/elements,domob1812/bitcoin,andreaskern/bitcoin,jamesob/bitcoin,namecoin/namecoin-core,dscotese/bitcoin,bitcoin/bitcoin,anditto/bitcoin,bitcoinsSG/bitcoin,namecoin/namecoin-core,namecoin/namecoin-core,domob1812/bitcoin,rnicoll/bitcoin,GroestlCoin/GroestlCoin,kallewoof/bitcoin,qtumproject/qtum,GroestlCoin/GroestlCoin,rnicoll/bitcoin,sstone/bitcoin,ElementsProject/elements,achow101/bitcoin,sstone/bitcoin,jambolo/bitcoin,ajtowns/bitcoin,lateminer/bitcoin,dscotese/bitcoin,pataquets/namecoin-core,domob1812/bitcoin,anditto/bitcoin,tecnovert/particl-core,Xekyo/bitcoin,fanquake/bitcoin,sipsorcery/bitcoin,andreaskern/bitcoin,apoelstra/bitcoin,GroestlCoin/GroestlCoin,Xekyo/bitcoin,sipsorcery/bitcoin,GroestlCoin/GroestlCoin,domob1812/namecore,rnicoll/bitcoin,apoelstra/bitcoin,mm-s/bitcoin,GroestlCoin/bitcoin,jlopp/statoshi,qtumproject/qtum,prusnak/bitcoin,domob1812/bitcoin,mm-s/bitcoin,namecoin/namecore,ElementsProject/elements,mruddy/bitcoin,bitcoinknots/bitcoin,sipsorcery/bitcoin,fujicoin/fujicoin,achow101/bitcoin,rnicoll/bitcoin,GroestlCoin/GroestlCoin,namecoin/namecore,ElementsProject/elements,MarcoFalke/bitcoin,GroestlCoin/bitcoin,fanquake/bitcoin,kallewoof/bitcoin,bitcoinsSG/bitcoin,Xekyo/bitcoin,particl/particl-core,namecoin/namecoin-core,JeremyRubin/bitcoin,jlopp/statoshi,mm-s/bitcoin,JeremyRubin/bitcoin,dscotese/bitcoin,namecoin/namecoin-core,ajtowns/bitcoin,ElementsProject/elements,fanquake/bitcoin,qtumproject/qtum,prusnak/bitcoin,andreaskern/bitcoin,rnicoll/bitcoin,achow101/bitcoin,bitcoin/bitcoin,fanquake/bitcoin,ajtowns/bitcoin,qtumproject/qtum,bitcoinsSG/bitcoin,qtumproject/qtum,GroestlCoin/bitcoin,sstone/bitcoin,Xekyo/bitcoin,jambolo/bitcoin,particl/particl-core,domob1812/namecore,pataquets/namecoin-core,MarcoFalke/bitcoin,MarcoFalke/bitcoin,jambolo/bitcoin,domob1812/namecore,bitcoin/bitcoin,sstone/bitcoin,tecnovert/particl-core,particl/particl-core,sstone/bitcoin,sipsorcery/bitcoin,fanquake/bitcoin,achow101/bitcoin,apoelstra/bitcoin,anditto/bitcoin,qtumproject/qtum,instagibbs/bitcoin,jamesob/bitcoin,MarcoFalke/bitcoin,anditto/bitcoin,ajtowns/bitcoin,jamesob/bitcoin,Xekyo/bitcoin,yenliangl/bitcoin,JeremyRubin/bitcoin,fujicoin/fujicoin,qtumproject/qtum,andreaskern/bitcoin,prusnak/bitcoin,dscotese/bitcoin,pataquets/namecoin-core,apoelstra/bitcoin,GroestlCoin/bitcoin,GroestlCoin/bitcoin,AkioNak/bitcoin,JeremyRubin/bitcoin,domob1812/namecore,bitcoin/bitcoin,bitcoinknots/bitcoin,jamesob/bitcoin,AkioNak/bitcoin,tecnovert/particl-core,kallewoof/bitcoin,lateminer/bitcoin,AkioNak/bitcoin,yenliangl/bitcoin,bitcoinsSG/bitcoin,domob1812/namecore,particl/particl-core,jlopp/statoshi,GroestlCoin/GroestlCoin,particl/particl-core,bitcoin/bitcoin,fujicoin/fujicoin,lateminer/bitcoin,andreaskern/bitcoin,jambolo/bitcoin,bitcoinknots/bitcoin,mruddy/bitcoin,ElementsProject/elements,domob1812/namecore