`pipenv install` timing out on RPi - python-3.x

Question

I'm trying to bring up [pipenv][1] on a Raspberry Pi Zero W. The symptom I'm seeing is that pexpect times out when trying to create a tutorial project.
Admittedly, the RPi is a small machine, but I was monitoring memory usage and swap space during the process, and it wasn't running out of memory or swap.
Any idea what it was trying to do? Or how I should debug this? Here's the stack trace:
pi#blue-server:~/testdir $ pipenv install requests
Creating a virtualenv for this project…
Using /usr/bin/python3 (3.5.3) to create virtualenv…
Traceback (most recent call last):
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/pexpect/expect.py", line 109, in expect_loop
return self.timeout()
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/pexpect/expect.py", line 82, in timeout
raise TIMEOUT(msg)
pexpect.exceptions.TIMEOUT: <pexpect.popen_spawn.PopenSpawn object at 0xb555c950>
searcher: searcher_re:
0: EOF
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/home/pi/.local/bin/pipenv", line 11, in <module>
sys.exit(cli())
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/click/core.py", line 722, in __call__
return self.main(*args, **kwargs)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/click/core.py", line 697, in main
rv = self.invoke(ctx)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/click/core.py", line 1066, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/click/core.py", line 895, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/click/core.py", line 535, in invoke
return callback(*args, **kwargs)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/cli.py", line 478, in uninstall
keep_outdated=keep_outdated,
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/core.py", line 2077, in do_uninstall
ensure_project(three=three, python=python)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/core.py", line 620, in ensure_project
three=three, python=python, site_packages=site_packages
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/core.py", line 569, in ensure_virtualenv
do_create_virtualenv(python=python, site_packages=site_packages)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/core.py", line 936, in do_create_virtualenv
click.echo(crayons.blue(c.out), err=True)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/delegator.py", line 99, in out
self.__out = self._pexpect_out
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/delegator.py", line 87, in _pexpect_out
result += self.subprocess.read()
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/pexpect/spawnbase.py", line 441, in read
self.expect(self.delimiter)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/pexpect/spawnbase.py", line 341, in expect
timeout, searchwindowsize, async_)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/pexpect/spawnbase.py", line 369, in expect_list
return exp.expect_loop(timeout)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/pexpect/expect.py", line 119, in expect_loop
return self.timeout(e)
File "/home/pi/.local/lib/python3.5/site-packages/pipenv/vendor/pexpect/expect.py", line 82, in timeout
raise TIMEOUT(msg)
pexpect.exceptions.TIMEOUT: <pexpect.popen_spawn.PopenSpawn object at 0xb553a710>
searcher: searcher_re:
0: EOF
<pexpect.popen_spawn.PopenSpawn object at 0xb553a710>
searcher: searcher_re:
0: EOF
Here's the environment info:
pi#blue-server:~/foo $ uname -a
Linux blue-server 4.14.34+ #1110 Mon Apr 16 14:51:42 BST 2018 armv6l GNU/Linux
pi#blue-server:~/foo $ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description: Raspbian GNU/Linux 9.4 (stretch)
Release: 9.4
Codename: stretch
pi#blue-server:~/foo $ cat /etc/os-release
PRETTY_NAME="Raspbian GNU/Linux 9 (stretch)"
NAME="Raspbian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"
pi#blue-server:~/foo $ free -m
total used free shared buff/cache available
Mem: 433 26 260 3 145 353
Swap: 99 0 99
additional info
I noticed it was timing out inside of a subprocess call. Using pdb, I traced it down to the command:
<Command ['/usr/bin/python3.5', '-m', 'pipenv.pew', 'new', 'foo-su43ObVR', '-d', '-p', '/usr/bin/python3.5']>
I tried replicating that call from the command line and it completed without error:
pi#blue-server:~/foo $ /usr/bin/python3.5 -m pipenv.pew new 'asdf' -d -p /usr/bin/python3.5
Already using interpreter /usr/bin/python3.5
Using base prefix '/usr'
New python executable in /home/pi/.local/share/virtualenvs/asdf/bin/python3.5
Also creating executable in /home/pi/.local/share/virtualenvs/asdf/bin/python
Installing setuptools, pip, wheel...done.
That seems hopeful, but I still don't know what causes the timeout.

Answer 1

TL;DR: the fix is to extend the timeout
Solved it. Because the RPi Zero is slow, it was timing out. Taking a clue from the discussion on github, I noticed that its now possible to extend the default timeout with environment variables. So this solved the problem:
pi#blue-server:~/testdir $ export PIPENV_TIMEOUT=500
pi#blue-server:~/testdir $ pipenv install requests