Make fetch fail on 404.

lib/spack/spack/stage.py

@@ -224,6 +224,7 @@ def fetch_from_url(self, url):
         # Run curl but grab the mime type from the http headers
         headers = spack.curl('-#',        # status bar
                              '-O',        # save file to disk
+                             '-f',        # fail on >400 errors
                              '-D', '-',   # print out HTML headers
                              '-L', url,
                              return_output=True, fail_on_error=False)
@@ -233,6 +234,10 @@ def fetch_from_url(self, url):
             if self.archive_file:
                 os.remove(self.archive_file)
 
+            if spack.curl.returncode == 22:
+                # This is a 404.  Curl will print the error.
+                raise FailedDownloadError(url)
+
             if spack.curl.returncode == 60:
                 # This is a certificate error.  Suggest spack -k
                 raise FailedDownloadError(