Hello!

I recently installed Guix on a foreign distro (Ubuntu 16.04), but am
unable to run `guix pull` after updating from 0.13.0 to 'master'.

--8<---------------cut here---------------start------------->8---
marius@uer:~$ guix pull --branch=core-updates # master also fails
Updating from Git repository at 'https://git.savannah.gnu.org/git/guix.git'...
Building from Git commit 2718a9cd096d0f5ae4b23cc0814a42aee5cf3c4d...
substitute: updating list of substitutes from 'https://mirror.hydra.gnu.org'... 100.0%
The following derivation will be built:
   /gnu/store/h01qr32ac80p7dl33llbw9yjl7y7ci8d-guix-latest.drv
copying and compiling to '/gnu/store/k4wrbdf8xk5ac8zz9fnsw1jghgf98gx4-guix-latest' with Guile 2.2.2...
loading...       25.3% of 620 filesrandom seed for tests: 1503514620
loading...       99.8% of 620 files
compiling...     93.4% of 620 filesice-9/threads.scm:289:22: In procedure loop:
ice-9/threads.scm:289:22: Syntax error:
guix/grafts.scm:267:2: return: return used outside of 'with-monad' in form (return result)

Some deprecated features have been used.  Set the environment
variable GUILE_WARN_DEPRECATED to "detailed" and rerun the
program to get more information.  Set it to "no" to suppress
this message.
builder for `/gnu/store/h01qr32ac80p7dl33llbw9yjl7y7ci8d-guix-latest.drv' failed with exit code 1
guix pull: error: build failed: build of `/gnu/store/h01qr32ac80p7dl33llbw9yjl7y7ci8d-guix-latest.drv' failed
--8<---------------cut here---------------start------------->8---

I've also seen this error (once):

--8<---------------cut here---------------end--------------->8---
compiling...     93.4% of 622 filesice-9/threads.scm:289:22: In procedure loop:
ice-9/threads.scm:289:22: Syntax error:
guix/scripts.scm:119:6: >>=: >>= (bind) used outside of 'with-monad' in form (>>= (maybe-build (list derivation) #:use-substitutes? use-substitutes? #:dry-run? dry-run?) (lambda (unused-value)
(mbegin %store-monad (return (show-derivation-outputs derivation)))))
--8<---------------cut here---------------end--------------->8---

This is a Broadwell system with 20 physical cores + HT and 192GB RAM.

Oddly, the initial pull from 0.13.0 went okay.  After that it
consistently fails like above around 93.4%.  What's going on here?

Compiling a git checkout "manually" works, FWIW.