Change percentage bars to use an explicit exception for value checks

[kevinlondon]

The percentage bars will now use an AssertionError directly if the provided values are outside of the expected range (0-100 inclusive).

I was using Bandit to check for potential vulnerabilities in a few popular Python projects and this came up as a warning:

>> Issue: Use of assert detected. The enclosed code will be removed when compiling to optimised byte code.
    Severity: Low   Confidence: High
    Location: glances/glances/outputs/glances_bars.py:72
 70      @percent.setter
 71      def percent(self, value):
 72          assert value >= 0
 73          assert value <= 100
 74          self.__percent = value

As per the warning, assert statements are stripped out if compiling with optimized bytecode (-O option) in Python. Here's a StackOverflow question with a little discussion and the original Python docs.

Oh, as a quick postscript, these tests run fine on OSX, so perhaps the Linux checks could be made to include OSX when running the tests?

[asergi]

Hi @kevinlondon,

Thanks for your contribution. I manually merged the PR into develop with commit 2b1b80c.

I guess those assert statements were added for debugging purposes and then left there.
About the tests, I will have a look later.

Again, thanks for your contribution.

[asergi]

Tests unblocked: 837193e.