rails app with pow and rvm: sudden pow error starting app

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.