title: gdc error "Error: module file is in file 'file.d' which cannot be read"
body: <p>I have searched and have seen similar errors but nothing specific as to how to fix this error. Using gdc (D compiler) I get this error message on my crunchbang debian linux machine:</p>
  
  <pre><code>gdc main.d fasta.d utilities.d
  utilities.d:3: Error: module file is in file 'file.d' which cannot be read
  import path[0] = /usr/include/d2/4.6/x86_64-linux-gnu
  import path[1] = /usr/include/d2/4.6
  utilities.d:3: Error: module file is in file 'file.d' which cannot be read
  import path[0] = /usr/include/d2/4.6/x86_64-linux-gnu
  import path[1] = /usr/include/d2/4.6
  </code></pre>
  
  <p>This is after freshly installing gdc with apt-get install.</p>