Maybe you need to do a
!mkdir -p {path}
in colab to create the directory /root/.fastai/archive/bluebook. path is specified in path = URLs.path('bluebook'), pointing to /root/.fastai/archive/bluebook.
As a side note, URLs.path(some_path) in colab (as of now at least: colab’s os Ubuntu 18.04.5 LTS, fastai 2.0.16) always points to '/root/.fastai/archive/'+some_path.splite('/')[-1]) , for example
some_path = '/content/drive/My Drive/datasets/bluebook'
URLs.path(some_path) # /root/.fastai/archive/bluebook
while URLs.path(some_path) in Windows behaves as expected.