travis: build_package: use `which`

dvc: bump to 0.50.1

appveyor: don't install dvc as editable

version: fix typo

dvc: bump to 0.41.2

dvc: bump to 0.41.1

dvc: bump to 0.41.0

dvc: bump to 0.40.7

dvc: bump to 0.40.6

dvc: bump to 0.40.5