Pretty-print HTTP errors when downloading a file.

emsdk

@@ -114,6 +114,7 @@ def download_file(url, dstpath, download_even_if_exists=False):
   if os.path.exists(file_name) and not download_even_if_exists:
     print "File '" + file_name + "' already downloaded, skipping."
     return True
+  try:
     u = urllib2.urlopen(url)
     mkdir_p(os.path.dirname(file_name))
     f = open(file_name, 'wb')
@@ -135,6 +136,9 @@ def download_file(url, dstpath, download_even_if_exists=False):
         print status,
 
     f.close()
+  except urllib2.HTTPError, e:
+    print "HTTP error with URL '" + url + "': " + str(e)
+    return False
   return True
 
 def run_get_output(cmd, cwd=None):