Wikitext datasets do not have valid.csv as referred in 35_tutorial_wikitext

[kdorichev]

Wikitext datasets (WIKITEXT, WIKITEXT_TINY) do not have *.txt files, but *.csv, and no valid.csv, as expected/referred to in the 35_tutorial_wikitext notebook:

path = untar_data(URLs.WIKITEXT_TINY)
!ls $path
test.csv  train.csv
...
val_txt = read_file(path/'valid.txt')

[kdorichev]

Also PR submitted to update correct URLs to the WIKITEXT* datasets.

[sgugger]

Fixed, our dataset is different from the original and I had built the tutorial on the original.