relnotes: copy "next" to "5.7" and clear "next"
The same procedure as every year^Wcycle.
Differential Revision: https://phab.mercurial-scm.org/D9909
from__future__importabsolute_importfrommercurial.i18nimport_frommercurialimportchangegroup,error,extensionsdefabort(orig,*args,**kwargs):raiseerror.Abort(_('this is an exercise'))defuisetup(ui):extensions.wrapfunction(changegroup,'getbundler',abort)