title: "Error running command: Build script returned non-zero exit code" when deploying Gatsby JS site to Netlify
body: <p>I recently came across Gatsby JS (<a href="https://github.com/gatsbyjs/gatsby" rel="noreferrer">https://github.com/gatsbyjs/gatsby</a>) and decided to build my portfolio site on top of the generator.</p>
  
  <p>So I forked their starter site (gatsby-starter-default) and built my portfolio with it (<a href="https://github.com/ArchieHicklin/Archie" rel="noreferrer">https://github.com/ArchieHicklin/Archie</a>)</p>
  
  <p>Locally (using '<code>gatsby develop</code>') it runs fine - but when I deploy to Netlify with '<code>gatsby build</code>' I get this error:</p>
  
  <pre><code>11:30:58 AM: Build started
  11:30:59 AM: Fetching cached dependencies
  11:30:59 AM: Expected build cache - but failed to find it
  11:30:59 AM: No cached dependencies found. Cloning fresh repo
  11:30:59 AM: git clone git@github.com:ArchieHicklin/Archie /mnt/build-work/1475033459125476884/repo
  11:31:00 AM: git remote rm origin /mnt/build-work/1475033459125476884/repo
  11:31:00 AM: Preparing Branch
  11:31:01 AM: Building site
  11:31:01 AM: Running build command
  11:31:02 AM: Running Build
  11:31:02 AM: Building
  11:31:03 AM: 0.0%
  11:31:03 AM: 1.2%
  11:31:04 AM: ## 3.6%
  11:31:04 AM: ##### 7.
  11:31:04 AM: 0%
  11:31:04 AM: ######## 12.5%
  11:31:04 AM: ##############
  11:31:04 AM:
  11:31:04 AM: 20.7%
  11:31:04 AM: ###################
  11:31:04 AM: 27.0%
  11:31:04 AM: ############################### 44.3%
  11:31:04 AM: ################################################## 70.0%
  11:31:04 AM: ############################################################# 86.1%
  11:31:04 AM: ########################################################################
  11:31:04 AM: 100.0%
  11:31:05 AM: 
  11:31:05 AM: Computing checksum with sha256sum
  11:31:05 AM: Checksums matched!
  11:31:06 AM: Using version v4.4.2 of node
  11:31:06 AM: Using /opt/buildhome/.rvm/gems/ruby-2.1.2
  11:31:06 AM: Installing npm modules
  11:31:07 AM: NPM modules installed
  11:31:08 AM: /opt/build/build.sh: line 232: gatsby: command not found
  11:31:08 AM: Cached node modules
  11:31:08 AM: Cleaning up docker container
  11:31:08 AM: Error running command: Build script returned non-zero exit code: 127
  11:31:08 AM: Error running command: Build script returned non-zero exit code: 127
  </code></pre>
  
  <p>Have done all the standard things like reinstall node and npm (as I thought it may be an issue) but, after a few weeks, I am absolutely stumped as to what the issue is. Likewise, there isn't a huge amount of documentation online so fairly stuck as to where to even start with tackling this issue.</p>
  
  <p>Any help (even pointers in where to start re debugging) would be really really appreciated!</p>