title: R studio Mac Proxy issue
body: <p>I have downloaded and installed R  (3.4.1)and R studio (1.0.153) on MAC OS ( El Captain). I am facing trouble setting up the proxy. I am trying to install some packages from CRAN.</p>
  
  <p>I referred to <a href="https://support.rstudio.com/hc/en-us/articles/200488488-Configuring-R-to-Use-an-HTTP-or-HTTPS-Proxy" rel="nofollow noreferrer">https://support.rstudio.com/hc/en-us/articles/200488488-Configuring-R-to-Use-an-HTTP-or-HTTPS-Proxy</a></p>
  
  <p>I was able to set up proxy and used properties
  http_proxy=<a href="http://MYSERVER:MYPORT" rel="nofollow noreferrer">http://MYSERVER:MYPORT</a>
  http_proxy_user=user:passwd</p>
  
  <p>I enabled options(internet.info = 0) option to get a trace of internet access from R Studio.
  While the proxy server set up looks good in logs, its not able to get authentication.</p>
  
  <p>Here are the logs:</p>
  
  <pre><code>Connected to MYSERVER  port MYPORT (#0)
  &gt; GET http://cran.rstudio.com/src/contrib/PACKAGES.gz HTTP/1.1
  Host: cran.rstudio.com
  User-Agent: R (3.4.1 x86_64-apple-darwin15.6.0 x86_64 darwin15.6.0)
  Accept: */*
  Proxy-Connection: Keep-Alive
  Pragma: no-cache
  
  * The requested URL returned error: 407 Proxy Authentication Required
  * Closing connection 0
  Warning: unable to access index for repository http://cran.rstudio.com/src/contrib:
    cannot open URL 'http://cran.rstudio.com/src/contrib/PACKAGES'
  </code></pre>
  
  <p>(Please note: I have replaced the proxy server and port )</p>
  
  <p>I tried changing the 
  http_proxy_user=ask</p>
  
  <p>As suggested in one of the work around I read, but that also didn't work. </p>
  
  <p>Could anyone suggest how to set up proxy authentication properly in R studio on Mac?</p>
  
  <p>I have Eclipse installed on my local using the same proxy port and authentication and it is able to download stuff fine.</p>
  
  <p>I am able to hit the url <a href="http://cran.rstudio.com/src/contrib/PACKAGES.gz" rel="nofollow noreferrer">http://cran.rstudio.com/src/contrib/PACKAGES.gz</a> directly in firefox.</p>