[Rd] Feature request: report the url if 404 error occurs

[Seth Falcon]

Currently, the connection code does not include the URL in the warning
message when a 404 response is received:

myUrl = "http://www.r-project.org/ABadPage.html"
con = url(myUrl)
readLines(con)

  Error in readLines(con) : cannot open the connection
  In addition: Warning message:
  cannot open: HTTP status was '404 Not Found' 

Would it be possible (and desirable) to include the URL in the warning
message?  Here's an example:

Error in readLines(con) : cannot open the connection
In addition: Warning message:
cannot open 'http://www.r-project.org/ABadPage.html': HTTP status was '404 Not Found' 


+ seth