Description of problem:
Git repository content:

  ls -l /var/tmp/puppet-modules/
  total 8
  drwxr-xr-x. 7 root root 4096 Nov  4 21:22 puppetlabs-stdlib
  -rw-r--r--. 1 root root   50 Nov  4 21:22 README.md

There is an error, because the "paths" list will contain an empty element after running find on 'Modulefile' puppet module build is called with an empty path.

pulp-puppet-module-builder --working-dir=/var/tmp/ --output-dir=/puppet-modules --url=https://puppet%40acceleris.ch:Changeme12@gitlab.kmu4u.ch/puppet/puppet-modules.git --branch=master --clean
rm -rf /var/tmp/puppet-modules.git
cd /var/tmp/
git clone --recursive https://puppet%40acceleris.ch:Changeme12@gitlab.kmu4u.ch/puppet/puppet-modules.git
cd puppet-modules
git status
git remote show -n origin
git fetch
git fetch --tags
git checkout master
git pull
find . -name Modulefile
find . -name metadata.json
Pahts: 
['', './puppetlabs-stdlib/metadata.json']
Modules: 
set(['', './puppetlabs-stdlib'])
puppet module build 
Error: Unable to find module root at /var/tmp/puppet-modules or parent directories
Error: Try 'puppet help module build' for usage


Version-Release number of selected component (if applicable):
pulp-puppet-tools-2.6.0.16-1.el7sat.noarch

How reproducible:
Every time.

Steps to Reproduce:
1. Create git repo
2. Add puppet modules with 'metadata.json'. Do not add modules with 'Modulefile'
3. Attempt to use pulp-puppet-module-builder to build all module in the repo.

Actual results:
pulp-puppet-module-builder --working-dir=/var/tmp/ --output-dir=/puppet-modules --url=https://puppet%40acceleris.ch:Changeme12@gitlab.kmu4u.ch/puppet/puppet-modules.git --branch=master --clean
rm -rf /var/tmp/puppet-modules.git
cd /var/tmp/
git clone --recursive https://puppet%40acceleris.ch:Changeme12@gitlab.kmu4u.ch/puppet/puppet-modules.git
cd puppet-modules
git status
git remote show -n origin
git fetch
git fetch --tags
git checkout master
git pull
find . -name Modulefile
find . -name metadata.json
Pahts: 
['', './puppetlabs-stdlib/metadata.json']
Modules: 
set(['', './puppetlabs-stdlib'])
puppet module build 
Error: Unable to find module root at /var/tmp/puppet-modules or parent directories
Error: Try 'puppet help module build' for usage

Expected results:
All puppet modules in the git repo should be built.

Additional info:
Can be fixed by removing empty entries from the list before iterating to execute 'puppet module build'.

https://github.com/pulp/pulp_puppet/pull/200