title: Reading Excel: evaluation error with zip file '..file.xlsx' cannot be opened
body: <p>I am using R with <code>readxl</code> package.  I try to import an Excel file with the following command:</p>
  
  <pre><code>library(readxl)
  city_codes &lt;- read_excel("./data/file.xlsx", sheet = "city_codes")
  </code></pre>
  
  <p>It says it is a zip file and cannot be opened:</p>
  
  <blockquote>
  <pre><code>Error in sheets_fun(path) : 
  Evaluation error: zip file './data/file.xlsx' cannot be opened.
  </code></pre>
  </blockquote>
  
  <p>Any ideas?</p>