anchor.diff:  
   buildPythonPackage rec {
     pname = "PyLTI";
  -  version = "0.4.1";
  +  version = "0.5.1";
   
     disabled = !isPy27;
   
  
positive.code: 
    propagatedBuildInputs = [ httplib2 oauth oauth2 semantic-version ];
    checkInputs = [
      flask httpretty oauthlib pyflakes pytest_27 pytestcache pytestcov covCore
      pytestflakes pytestpep8 sphinx mock
    ];
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "076llj10j85zw3zq2gygx2pcfqi9rgcld5m4vq1iai1fk15x60fz";
    };
  
    meta = {
  
negative.code: , httpretty
  , oauthlib
  , pyflakes
  , pytest
  , pytestcache
  , pytestcov
  , covCore
  