title: Can't install devtools
body: <p>I can't install devtools: </p>
  
  <pre><code>if (!require("devtools")) install.packages("devtools") 
  devtools::install_github("rstudio/httpuv")
  </code></pre>
  
  <p>produces:</p>
  
  <blockquote>
    <p>ERROR: dependency 'pkgload' is not available for package 'devtools' *
    removing 'C:/Users/R/win-library/3.3/devtools'</p>
  </blockquote>
  
  <pre><code>install.packages('pkgload')
  </code></pre>
  
  <p>creates: </p>
  
  <blockquote>
    <p>Package which is only available in source form, and may need
    compilation of C/C++/Fortran: ‘pkgload’ These will not be installed –</p>
  </blockquote>