rails app with pow and rvm: sudden pow error starting app - ruby-on-rails

Question

Everything was running fine and suddenly (with no changes to the setup) pow can no longer start the app!
Here's my setup:
rails 4.2
rvm 1.28.0 (with .ruby-version and .ruby-gemset)
pow 0.5.0
Here is what I saw in my browser (Chrome)
Here is the pow log:
[Thu Jan 19 2017 19:35:01 GMT-0800 (PST)] ERROR '/Users/john/dev/savvy/aristotle/.powrc' failed to load:
true &&
source '/Users/john/dev/savvy/aristotle/.powrc' > /dev/null &&
env > '/var/folders/jg/_01lx50x3tngs9br0dkmq_mh0000gn/T/pow.91337.1484883301131.60339'
[Thu Jan 19 2017 19:35:01 GMT-0800 (PST)] ERROR stdout:
[Thu Jan 19 2017 19:35:01 GMT-0800 (PST)] ERROR stderr: /Users/john/.rvm/scripts/rvm: line 12: uname: command not found
/Users/john/.rvm/scripts/rvm: line 15: ps: command not found
/Users/john/dev/savvy/aristotle/.powrc: line 2: rvm: command not found
NOTICE that while the pow log says .powrc failed to load, the logged error says rvm: command not found. However rvm was found right before this pow error suddenly occurred.
Here is the .powrc (which was working fine before the error):
if [ -f "${rvm_path}/scripts/rvm" ]; then
source "${rvm_path}/scripts/rvm"
if [ -f ".rvmrc" ]; then
source ".rvmrc"
elif [ -f ".ruby-version" ] && [ -f ".ruby-gemset" ]; then
rvm use `cat .ruby-version`#`cat .ruby-gemset`
elif [ -f ".ruby-version" ]; then
rvm use `cat .ruby-version`
fi
fi
Here is my rvm info from within the root of the rails app:
ruby-2.2.1#savvy:
system:
uname: "Darwin flat-top.local 14.0.0 Darwin Kernel Version 14.0.0: Fri Sep 19 00:26:44 PDT 2014; root:xnu-2782.1.97~2/RELEASE_X86_64 x86_64"
system: "osx/10.10/x86_64"
bash: "/bin/bash => GNU bash, version 3.2.53(1)-release (x86_64-apple-darwin14)"
zsh: "/bin/zsh => zsh 5.0.5 (x86_64-apple-darwin14.0)"
rvm:
version: "rvm 1.28.0 (latest) by Wayne E. Seguin <wayneeseguin#gmail.com>, Michal Papis <mpapis#gmail.com> [https://rvm.io/]"
updated: "1 hour 52 minutes 59 seconds ago"
path: "/Users/john/.rvm"
ruby:
interpreter: "ruby"
version: "2.2.1p85"
date: "2015-02-26"
platform: "x86_64-darwin14"
patchlevel: "2015-02-26 revision 49769"
full_version: "ruby 2.2.1p85 (2015-02-26 revision 49769) [x86_64-darwin14]"
homes:
gem: "/Users/john/.rvm/gems/ruby-2.2.1#savvy"
ruby: "/Users/john/.rvm/rubies/ruby-2.2.1"
binaries:
ruby: "/Users/john/.rvm/rubies/ruby-2.2.1/bin/ruby"
irb: "/Users/john/.rvm/rubies/ruby-2.2.1/bin/irb"
gem: "/Users/john/.rvm/rubies/ruby-2.2.1/bin/gem"
rake: "/Users/john/.rvm/gems/ruby-2.2.1#savvy/bin/rake"
environment:
PATH: "/Users/john/.rvm/gems/ruby-2.2.1#savvy/bin:/Users/john/.rvm/gems/ruby-2.2.1#global/bin:/Users/john/.rvm/rubies/ruby-2.2.1/bin:/Users/john/.rvm/bin:/Users/john/dev/savvy/aristotle/.direnv/bundler-bin:/Users/john/dev/savvy/aristotle/.direnv/bin:/Users/john/dev/savvy/aristotle/.direnv/ruby/bin:/Users/john/.pyenv/shims:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin"
GEM_HOME: "/Users/john/.rvm/gems/ruby-2.2.1#savvy"
GEM_PATH: "/Users/john/.rvm/gems/ruby-2.2.1#savvy:/Users/john/.rvm/gems/ruby-2.2.1#global"
MY_RUBY_HOME: "/Users/john/.rvm/rubies/ruby-2.2.1"
IRBRC: "/Users/john/.rvm/rubies/ruby-2.2.1/.irbrc"
RUBYOPT: ""
gemset: "savvy"
To the best of my recollection, the error occurred when I was adding routes, controller actions and views for a new feature in this rails app.
Here is what I have tried so far:
Remove the changes to the app I made immediately before the error occurred
Rebuilt the pow symlink
Stopped and started the pow daemon
rvm cleanup all
rvm get stable
reboot
remove and re-install pow
QUESTION: In an operational rails/pow/rvm system with no setup changes, why does pow suddenly fail to start the app?
I'm out of ideas.