Run wget with -nv instead of -q, so it will display HTTP errors.

This adds one extra line of output when a download is successful,
after the progress bar. I don't much like that, but wget does not provide a
way to show HTTP errors without it.

doc/todo/more_of_diagnostic_information_in_case_of_failures_into_returned_json/comment_1_0eeb859b57d4dc8a3c9c9c3c4f70bb45._comment

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+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2017-02-20T18:50:18Z"
+ content="""
+Probably wget is just failing to download the url sometimes.
+Eg, `git annex addurl http://localhost/dne` fails with the same not useful
+output.
+
+wget is run with -q, which is the only way to turn off all its informational
+messages, but unfortunately that also turns off display of HTTP error messages.
+
+Using -nv instead of -q would display HTTP errors,
+but also 1 extra line of output once the download is complete.
+I suppose that's worth the trade-off.
+"""]]

doc/todo/more_of_diagnostic_information_in_case_of_failures_into_returned_json/comment_2_82b851629c695084cbf62e2b636bcc91._comment

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+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 2"""
+ date="2017-02-20T19:15:18Z"
+ content="""
+In general, the --json output does include a "note" with any
+available message about why an operation failed. 
+
+Since wget outputs HTTP errors to stdout, there's no way to capture the actual
+message for json, and so swiching to wget -nv won't improve the json.
+(curl also outputs HTTP errors to stdout too, so it's no better)
+
+Short of using a HTTP library for url downloads in --json mode,
+I don't see a way to fix this. It would not be hard to use a HTTP library
+and propagate the HTTP errors into the json "note", but it might be hard to
+get resumption of partial downloads to work as well with a HTTP library as
+it works with wget.
+""]]