heroku run rake db:migrate ... rake aborted! No Rakefile found - ruby-on-rails

Question

When I run heroku run rake db:migrate, I receive the following error:
$ heroku run rake db:migrate
Running `rake db:migrate` attached to terminal... up, run.8507
rake aborted!
No Rakefile found (looking for: rakefile, Rakefile, rakefile.rb, Rakefile.rb)
/usr/local/lib/ruby/1.9.1/rake.rb:2367:in `raw_load_rakefile'
/usr/local/lib/ruby/1.9.1/rake.rb:2007:in `block in load_rakefile'
/usr/local/lib/ruby/1.9.1/rake.rb:2058:in `standard_exception_handling'
/usr/local/lib/ruby/1.9.1/rake.rb:2006:in `load_rakefile'
/usr/local/lib/ruby/1.9.1/rake.rb:1991:in `run'
/usr/local/bin/rake:31:in `<main>'
Other users have posted identical errors, but in their case they actually didn't have a Rakefile and it worked for them once they created one, or they were in the wrong directory. My app does have a Rakefile, in the correct directory and with all the proper text in it, and I am in my app's root directory.
This is what my Rakefile looks like:
# Add your own tasks in files placed in lib/tasks ending in .rake,
# for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
require File.expand_path('../config/application', __FILE__)
Rails.application.load_tasks
This is what "heroku run cat Rakefile" does:
$ heroku run cat Rakefile
Running `cat Rakefile` attached to terminal... up, run.9132
cat: Rakefile: No such file or directory

Answer 1

Whenever you are struggling with Heroku you should check your logs:
heroku logs
Scan through for any errors that you can google and/or get hints to what is going wrong.
If you are using git you can quickly search for errors with this:
git grep "whatever you want to search for"
You will then know where to find the file so you might try to verify that the rakefile actually exists with:
git grep rakefile
Sometimes it is easier to just start fresh and reset your database and reload your current schema with:
rake db:reset db:migrate all
This will destroy your db and then create it and then migrate your current schema:
rake db:drop db:create db:migrate
If you want to reset the heroku db
To drop the database, if you are using SHARED_DATABASE_URL:
heroku pg:reset DATABASE
To recreate the database with nothing in it:
heroku run rake db:migrate
To populate the database with your seed data:
heroku run rake db:seed