Capistrano: Gem bundler is not installed - ruby-on-rails

Question

Capistrano raises the error "ERROR: Gem bundler is not installed, run gem install bundler first."
But when I clone the project to /tmp/project of the targe server bundle runs (as root) smoothly.
The server is a Ubuntu 12.04.2 LTS, ruby was installed via rvm.
I added "source /usr/local/rvm/scripts/rvm" to the /root/.bashrc but it did not solve the problem.
require "bundler/capistrano"
set :application, 'myproject'
set :repository, "git#myproject.git"
set :branch, 'staging'
set :user, 'root'
set :domain, "mydomain"
set :deploy_to, "/var/webapps/#{application}"
role :web, domain # Your HTTP server, Apache/etc
role :app, domain # This may be the same as your `Web` server
role :db, domain, :primary => true # This is where Rails migrations will run
role :db, domain
default_run_options[:pty] = true
# [and then the tasks]
TIA.
EDIT
This very same deploy script worked in another server, with ruby installed in the same way. The only difference I remember is that that server was a CentOS.
Also tried rvm wrapper rvm current bundle bundle as suggested here
Edit 2
I compared the env command via ssh and via capistrano. The following env variables were missing when env was issued by capistrano:
__array_start=0
_first=0
_second=1
escape_flag=1
GEM_HOME=/usr/local/rvm/gems/ruby-1.9.3-p392
GEM_PATH=/usr/local/rvm/gems/ruby-1.9.3-p392:/usr/local/rvm/gems/ruby-1.9.3-p392#global
IRBRC=/usr/local/rvm/rubies/ruby-1.9.3-p392/.irbrc
LC_ADDRESS=pt_BR.UTF-8
LC_IDENTIFICATION=pt_BR.UTF-8
LC_MEASUREMENT=pt_BR.UTF-8
LC_MONETARY=pt_BR.UTF-8
LC_NAME=pt_BR.UTF-8
LC_NUMERIC=pt_BR.UTF-8
LC_PAPER=pt_BR.UTF-8
LC_TELEPHONE=pt_BR.UTF-8
LC_TIME=pt_BR.UTF-8
LESSCLOSE=/usr/bin/lesspipe %s %s
LESSOPEN=| /usr/bin/lesspipe %s
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lz=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.axa=00;36:*.oga=00;36:*.spx=00;36:*.xspf=00;36:
MY_RUBY_HOME=/usr/local/rvm/rubies/ruby-1.9.3-p392
RUBY_VERSION=ruby-1.9.3-p392
rvm_bin_path=/usr/local/rvm/bin
rvm_debug_clr=
rvm_error_clr=
rvm_notify_clr=
rvm_path=/usr/local/rvm
rvm_prefix=/usr/local
rvm_reset_clr=
rvm_version=1.19.5 (stable)
rvm_warn_clr=
The following env vars were different:
_=/usr/bin/env # ssh
_=/bin/sh # capistrano
LANG=en_US.UTF-8 # ssh
LANG=C # capistrano
LANGUAGE=en # ssh
LANGUAGE=C # capistrano
# ssh
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/rvm/bin
# capistrano
PATH=/usr/local/rvm/gems/ruby-1.9.3-p392/bin:/usr/local/rvm/gems/ruby-1.9.3-p392#global/bin:/usr/local/rvm/rubies/ruby-1.9.3-p392/bin:/usr/local/rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games

Answer 1

I had a similar problem with one of my setups, though I use rbenv to manage ruby versions. The issue was that bundler was not installed on the Ruby version my project was pointing to.
I did a quick check online and you have a few options:
run rvm gemset use global && gem install bundler (installs to
global version)
edit your /.bashrc ... something along those lines
([[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm")
Running gem env may show you that you are forcing a path, and you would then need to remove the entry from ~/.gemrc or /etc/gemrc
My 2-cents