package { 'puppet-lint': ensure => '1.1.0', provider => 'gem', }
Or, if you really must:
$ gem install puppet-lint
$ puppet-lint /etc/puppet/modules foo/manifests/bar.pp - ERROR: trailing whitespace found on line 1 apache/manifests/server.pp - WARNING: variable not enclosed in {} on line 56 ...
$ puppet-lint --fix /etc/puppet/modules foo/manifests/bar.pp - FIXED: trailing whitespace found on line 1 apache/manifests/server.pp - FIXED: variable not enclosed in {} on line 56 ...
Head on over to the checks page to see a description of each check and get some help on how to clear those errors.