Rails wants pg 0.10.0 but I can only install pg 0.10.1

I'm on Mac OS X. If I run sudo env ARCHFLAGS="-arch i386" gem install pg, it works just fine. However, I get this error when I try to visit my Rails project in the browser:

Could not find pg-0.10.0 in any of the sources (Bundler::GemNotFound)

If I then uninstall 0.10.1 and try to install 0.10.0, I get this:

$ sudo env ARCHFLAGS="-arch i386" gem install pg --version 0.10.0
Password:
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb
checking for pg_config... yes
Ruby cflags: "-arch i386 -g -Os -pipe -fno-common -DENABLE_DTRACE  -fno-common  -pipe -fno-common  "
MacOS X build: fixing architecture flags:
  using the value in ARCHFLAGS environment variable ("-arch i386").
  finding flags common to both Ruby and PostgreSQL...
  testing for architecture: "ppc"
  testing for architecture: "i386"
  common arch flags: -arch i386
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.开发者_Python百科  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby
    --with-pg
    --without-pg
    --with-pg-config
    --without-pg-config
    --with-pg-dir
    --without-pg-dir
    --with-pg-include
    --without-pg-include=${pg-dir}/include
    --with-pg-lib
    --without-pg-lib=${pg-dir}/lib


Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/pg-0.10.0 for inspection.
Results logged to /Library/Ruby/Gems/1.8/gems/pg-0.10.0/ext/gem_make.out

I don't care whether I find a way to make Rails accept pg 0.10.1 or if I find a way to install pg 0.10.0, but I need to do one or the other.

Is version 0.10.0 listed in your Gemfile.lock? If so, you should be able to update the version Rails is looking for by running bundle update pg, assuming your Gemfile doesn't also specify version 0.10.0.