pdfinvert.rb does not work if Inkscape can not access /tmp

Start by reproducing ruby pdfinvert.rb sheet01.pdf sheet01_inv.pdf with the supplied archive, then inspect pdfinvert.rb around line 222 and the Inkscape-related temporary-file handling. Done means the command completes successfully and produces the inverted PDF when Inkscape cannot access /tmp.

I really appreciate the work you put in the pdfinvert script. I searched long on the internet to find sth useful to invert pdf 😀
But I get an exception when executing. Here is the debug output:

▶ ruby pdfinvert.rb sheet01.pdf sheet01_inv.pdf          
Exception `Gem::LoadError' at /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/dependency.rb:319 - Could not find 'parallel' (>= 0) among 15 total gem(s)
Checked in 'GEM_PATH=/Users/renekud/.gem/ruby/2.3.0:/Library/Ruby/Gems/2.3.0:/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/gems/2.3.0', execute `gem env` for more information
Exception `Errno::ENOENT' at pdfinvert.rb:222 - No such file or directory @ rb_sysopen - input_0001.svg
pdfinvert.rb:222:in `initialize': No such file or directory @ rb_sysopen - input_0001.svg (Errno::ENOENT)
	from pdfinvert.rb:222:in `open'
	from pdfinvert.rb:222:in `invert'
	from pdfinvert.rb:354:in `block in <main>'
	from pdfinvert.rb:353:in `each'
	from pdfinvert.rb:353:in `rescue in <main>'
	from pdfinvert.rb:343:in `<main>'

I have the script in the same directory like the pdf that I want to invert. It would be wonderfull if we could fix this. Sadly I never did sth in ruby :D
Here are the files of the /tmp/pdfinvert folder:
pdfinvert_sheet01.zip