Revert "pythonPackages.psutil: 3.4.2 -> 4.3.0"

This reverts commit 86caec1b.

In this commit tests were re-enabled, but without correctly testing whether it could.
When a package builds it doesn't mean the tests are actually run. This is often seen when it says that 0 tests were run.
Typically this is because the test runner was invoked incorrectly.

By re-enabling the tests, a false impression is generated that the package is tested while in fact it isn't. Furthermore, the Python 3.5
package broke because the tests are invoked incorrectly.

cc @abbradar