PIP issue on Travis CI: "no such option: --system"

[gulyx]

Uncommenting the lines:

• L161
• L182
  will cause the following build error on Travis CI:

Usage:   
  pip install [options] <requirement specifier> [package-index-options] ...
  pip install [options] -r <requirements file> [package-index-options] ...
  pip install [options] [-e] <vcs project url> ...
  pip install [options] [-e] <local project path> ...
  pip install [options] <archive url/path> ...
no such option: --system
[ERROR] Command execution failed.

However on my local environment, I had to specify the --system option for pip both in build-jep and in build-xxhash. Following the discussions on other issues (e.g like haaska#52 or haaska#37 ), I realized that possibly I have locally updated "pip by means of pip" so that the installed version on my locals is not any more the "original" Debian used in Travis CI, or vice-versa.

For the moment I will keep the project configured for passing the build on Travis CI and I will uncomment only locally (and when needed) the option in the two arguments in the pom. Please do the same in case you are in the same circumstances. Specifically, replace

<!-- 	<argument>-REMOVE_THIS_SPACE-system</argument> -->

with

<argument>--system</argument>

[gulyx]

Possibly this ISSUE is solved by commit 74616c4