title: Adding a vignette stops devtools::check() from working
body: <p>I've been writing a personal package with reference to <a href="http://r-pkgs.had.co.nz/intro.html" rel="nofollow noreferrer">Hadley's guide</a>. However, adding a minimal vignette using <code>devtools::use_vignette()</code> seems to break <code>devtools::check()</code>.</p>
  
  <p>When I try to run <code>check()</code> I get one error:</p>
  
  <pre><code>file 'C:/path/temp/package/DESCRIPTION' is not in valid DCF format
  </code></pre>
  
  <p>and one warning:</p>
  
  <pre><code>In read.dcf(dfile, keep.white = .keep_white_description_fields) :
    cannot open compressed file 'C:/path/temp/package/DESCRIPTION', probable reason 'Permission denied'
  </code></pre>
  
  <p>I can successfully run <code>devtools::check()</code> if I delete the vignettes folder and <code>devtools::build_vignettes()</code> runs ok. </p>
  
  <p><strong>Edited to add:</strong>
  I wondered if this was an issue with trying run check from a network location, but I copied the project to <code>C:\R\package_name</code> and it still returns the same error. </p>
  
  <p>Curiously, this does appear to be machine dependent as I get the above error on my work machine, but not on my personal laptop. Work machine is win7, personal win10.</p>
  
  <p>DESCRIPTION is copied below</p>
  
  <pre><code>Package: pkg_nm
  Type: Package
  Title: A title
  Version: 0.0.0.9000
  Authors@R: person("name", "name", email = "emal@email.com", role = c("aut", "cre"))
  Description: Functions for working with data from my source.
  License: OGL
  LazyData: TRUE
  RoxygenNote: 5.0.1
  URL: [url here]
  BugReports: [url here]
  Imports:
      lubridate,
      stringr,
      dplyr,
      lazyeval,
      magrittr
  Collate:
      'my_function.R'
  Suggests: knitr,
      rmarkdown
  VignetteBuilder: knitr
  </code></pre>