### Please describe the problem.

Continuation of the prior brief troubleshooting in [devblog](http://git-annex.branchable.com/devblog/day_518__S3_versioning_finishing_touches/#comment-ced84e6126b523170638f36a73cdb4b1).

Joey:

> As to the problems you're having with that S3 remote, it looks like it does not have public=yes enabled in its configuration at all, which is why git-annex is failing to download from it. 

I do not think that is the case.  s3-PUBLIC has `public=yes`.  But it is entirely not clear why git-annex fails to download - no diagnostic error message at --debug level.  Please try yourself:

### What steps will reproduce the problem?

[[!format sh """
~datalad > git clone https://github.com/OpenNeuroDatasets/ds001419               
Cloning into 'ds001419'...
remote: Enumerating objects: 420, done.
remote: Counting objects: 100% (420/420), done.
remote: Compressing objects: 100% (232/232), done.
remote: Total 420 (delta 99), reused 418 (delta 97), pack-reused 0
Receiving objects: 100% (420/420), 37.43 KiB | 2.88 MiB/s, done.
Resolving deltas: 100% (99/99), done.

~datalad > cd ds001419 

~datalad/providers/openneuro/ds001419 > git annex enableremote s3-PUBLIC
(merging origin/git-annex into git-annex...)
(recording state in git...)
download failed: Not Found

  Remote origin not usable by git-annex; setting annex-ignore
enableremote s3-PUBLIC ok
(recording state in git...)

~datalad/providers/openneuro/ds001419 > git annex whereis sub-01/anat/sub-01_T1w.nii.gz                                                                                       
whereis sub-01/anat/sub-01_T1w.nii.gz (2 copies)  
  	303581cd-3c58-4a60-b685-42cae4314c68 -- root@1f69c4ed80cf:/datalad/ds001419
   	c21131c5-9e22-442d-a4d6-22d225603bc9 -- s3-PRIVATE

  The following untrusted locations may also have copies:
  	336309c0-d7f8-430e-bd2b-4bdc61e587cb -- [s3-PUBLIC]
ok

~datalad/providers/openneuro/ds001419 > git annex get --from s3-PUBLIC --debug sub-01/anat/sub-01_T1w.nii.gz
[2018-09-25 11:30:48.623186962] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","show-ref","git-annex"]
[2018-09-25 11:30:48.6294298] process done ExitSuccess
[2018-09-25 11:30:48.629531355] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","show-ref","--hash","refs/heads/git-annex"]
[2018-09-25 11:30:48.63678286] process done ExitSuccess
[2018-09-25 11:30:48.637035079] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","log","refs/heads/git-annex..a6e5981635fd80f9186e6aa840312a97153508a4","--pretty=%H","-n1"]
[2018-09-25 11:30:48.648701597] process done ExitSuccess
[2018-09-25 11:30:48.648965608] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","cat-file","--batch"]
[2018-09-25 11:30:48.649547391] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","cat-file","--batch-check=%(objectname) %(objecttype) %(objectsize)"]
[2018-09-25 11:30:48.655933893] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","ls-files","--cached","-z","--","sub-01/anat/sub-01_T1w.nii.gz"]
get sub-01/anat/sub-01_T1w.nii.gz (from s3-PUBLIC...) [2018-09-25 11:30:48.662890927] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","diff-tree","-z","--raw","--no-renames","-l0","-r","4b825dc642cb6eb9a060e54bf8d69288fbee4904","3bbd58c6720ad7a764409c219397a4e15e4ed77d","--"]
[2018-09-25 11:30:48.670609446] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","cat-file","--batch"]
[2018-09-25 11:30:48.672897086] chat: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","cat-file","--batch-check=%(objectname) %(objecttype) %(objectsize)"]
[2018-09-25 11:30:48.681427258] process done ExitSuccess
failed
[2018-09-25 11:30:48.740042089] process done ExitSuccess
[2018-09-25 11:30:48.740263179] process done ExitSuccess
[2018-09-25 11:30:48.740549287] process done ExitSuccess
[2018-09-25 11:30:48.740805353] process done ExitSuccess
git-annex: get: 1 failed

~datalad/providers/openneuro/ds001419 > git cat-file -p git-annex:remote.log
336309c0-d7f8-430e-bd2b-4bdc61e587cb bucket=openneuro.org datacenter=US encryption=none exporttree=yes fileprefix=ds001419/ host=s3.amazonaws.com name=s3-PUBLIC partsize=1GiB port=80 public=yes publicurl=yes storageclass=STANDARD type=S3 timestamp=1537889429.294083309s
c21131c5-9e22-442d-a4d6-22d225603bc9 bucket=openneuro-private datacenter=US encryption=none exporttree=yes fileprefix=ds001419/ host=s3.amazonaws.com name=s3-PRIVATE partsize=1GiB port=80 storageclass=STANDARD type=S3 timestamp=1531961539.924031958s

~datalad/providers/openneuro/ds001419 > git annex info
repository mode: indirect
trusted repositories: 0
semitrusted repositories: 5
	00000000-0000-0000-0000-000000000001 -- web
 	00000000-0000-0000-0000-000000000002 -- bittorrent
 	303581cd-3c58-4a60-b685-42cae4314c68 -- root@1f69c4ed80cf:/datalad/ds001419
 	3cf65be0-250d-4456-bfee-8501390e28c7 -- yoh@hopa:~/proj/datalad/providers/openneuro/ds001419 [here]
 	c21131c5-9e22-442d-a4d6-22d225603bc9 -- s3-PRIVATE
untrusted repositories: 1
	336309c0-d7f8-430e-bd2b-4bdc61e587cb -- [s3-PUBLIC]
transfers in progress: none
available local disk space: 1.76 gigabytes (+1 megabyte reserved)
local annex keys: 0
local annex size: 0 bytes
annexed files in working tree: 7
size of annexed files in working tree: 183.03 megabytes
bloom filter size: 32 mebibytes (0% full)
backend usage: 
	MD5E: 7

~datalad/providers/openneuro/ds001419 > git annex info s3-PUBLIC
uuid: 336309c0-d7f8-430e-bd2b-4bdc61e587cb
description: [s3-PUBLIC]
remote: s3-PUBLIC
trust: untrusted
cost: 200.0
type: S3
creds: not available
bucket: openneuro.org
endpoint: s3.amazonaws.com
port: 80
storage class: STANDARD
partsize: 1.07 gigabytes
public: yes
versioning: no
encryption: none
chunking: none
export: yes
remote annex keys: 27
remote annex size: 183.03 megabytes (+ 20 unknown size)

"""]]


may be it is somehow interaction with the fact that the bucket is versioned, although export happened with annex version which didn't support versioning?

It would be nice, before introducing versioning information as you outlined in the [comment](http://git-annex.branchable.com/devblog/day_518__S3_versioning_finishing_touches/#comment-01400aba452e6596e2b6b2967a0b9bc1) to enable access to the bucket at least to download the most recent version(s) of the file(s).

### What version of git-annex are you using? On what operating system?

6.20180913+git52-gdb1644808-1~ndall+1


[[!meta author=yoh]]
[[!tag projects/datalad]]

> Added an error message when download of an invalid url is attempted
> and also made the url be listed by --debug. [[done]] --[[Joey]]
