guix build gives `/homeless-shelter' exists; please remove it

[Phil Beadling]

Hi Guixers,

As of last night my Guix installation (on Ubuntu) is giving the following
error when trying to fetch a URL as part of the 'guix build'.  The error
does not happen when downloading the same package using 'guix download':

*guix build: error: directory `/homeless-shelter' exists; please remove it *

It seems to make no difference what the package or or where the URL is
fetched from, I can demonstrate it with any arbitrary file on any website
I've tried so far.

However, if I use 'guix download' I am able to download the package, and
then 'guix build' works as planned, using the copy stored by 'guix
download'.

Can anyone point to where I might look to delete the homeless-shelter - or
if this is perhaps a misleading error message?

I have no idea what triggered this - my installation has worked fine for
months - the only thing I can think is that I updated the version and hash
of a package definition in my local channel just before the problem was
noticed - this may of course be coincidence.

I've tried all the obvious stuff - guix pull, bouncing the daemon, etc.

Any ideas?

Thanks,
Phil

Here's one example - in order to randomly test a few download locations I
simply updated a package to download from a few locations I know to work
github, pypi, etc - here's an example - the package won't build because
it's hijacked - the point is it doesn't even download the pandas tar ball -
it fails immediately before it even downloads and expands the source.

I then replaced the URL with several other locations and got the same
result.

I also tried a few different package definitions too in case that was the
issue.


(define-public gurobipy-950
  (package/inherit gurobipy
                   (name "gurobipy-950")
                   (version "9.5.0")
                   (source (origin
                             (method url-fetch)
*                             (uri
"https://files.pythonhosted.org/packages/99/f0/f99700ef327e51d291efdf4a6de29e685c4d198cbf8531541fc84d169e0e/pandas-1.3.5.tar.gz
<https://files.pythonhosted.org/packages/99/f0/f99700ef327e51d291efdf4a6de29e685c4d198cbf8531541fc84d169e0e/pandas-1.3.5.tar.gz>")*
                             (sha256
                              (base32

 "17n2icl41jzkkhb4a8ksqgzqa92pqnk5xw7ackizd18nbmd2wm5v"))))))


substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
substitute: updating substitutes from 'https://bordeaux.guix.gnu.org'...
100.0%
The following derivations will be built:
   /gnu/store/pvaqlg8sap0z8b2hs8a2g617vx08rxpx-gurobipy-950-9.5.0.drv
*   /gnu/store/ng2kx8hbgsvch8ssa3bvs47sn50xcddz-pandas-1.3.5.tar.gz.drv*
*guix build: error: directory `/homeless-shelter' exists; please remove it*

now if I 'guix download' the pandas package first the build will continue
without the error.