text: Title: CI Tests fail due to NLTK download first byte timeout
  Body: **NLTK Downloader**
  
  Here is a sample of an NLTK download in progress:
  
  > [nltk_data]    | Downloading package twitter_samples to
  [nltk_data]    |     C:\Users\appveyor\AppData\Roaming\nltk_data...
  [nltk_data]    |   Unzipping corpora\twitter_samples.zip.
  [nltk_data]    | Downloading package omw to
  [nltk_data]    |     C:\Users\appveyor\AppData\Roaming\nltk_data...
  [nltk_data]    | Error downloading 'omw' from
  [nltk_data]    |     <https://raw.githubusercontent.com/nltk/nltk_data
  [nltk_data]    |     /gh-pages/packages/corpora/omw.zip>:   HTTP Error
  [nltk_data]    |     503: first byte timeout
  Error installing package. Retry? [n/y/e]
  
  There is a related issue:
  https://github.com/nltk/nltk/issues/1647
  
  Could cached NLTK downloads provide the necessary NLTK data with sufficient freshness?
  
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