set libsass version properly

[sebastian-brunner]

Currently in setup.py the libsass version is set to: libsass >= 0.15.0

However with e.g. libsass==0.20.0 you get the following output and css generation does not succeed.

earching for pytest-runner
Best match: pytest-runner 5.2
Processing pytest_runner-5.2-py2.7.egg

Using /home/seb/develop/rafcon/.eggs/pytest_runner-5.2-py2.7.egg
running build_sass
building 'rafcon' sass
WARNING on line 139, column 25 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %selected_items, :disabled` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 593, column 41 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked, :first-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 594, column 40 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked, :last-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 595, column 40 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked, :only-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 775, column 11 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend *, :link` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 876, column 41 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend button, :drop(active)` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 885, column 73 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked, :first-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 886, column 72 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked, :last-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 887, column 72 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked, :only-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 890, column 67 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked_vertical, :first-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 891, column 66 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked_vertical, :last-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 892, column 66 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %linked_vertical, :only-child` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 1037, column 30 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend *, :link, :selected` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 1212, column 35 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %selected-button, :active` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 1215, column 15 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %selected-button, .flat, :disabled` instead.
See http://bit.ly/ExtendCompound for details.

WARNING on line 1217, column 37 of /home/seb/develop/rafcon/source/rafcon/../../share/themes/RAFCON/sass/_common.scss:
Compound selectors may no longer be extended.
Consider `@extend %selected-button, :disabled, :checked` instead.
See http://bit.ly/ExtendCompound for details.

[sebastian-brunner]

Setting the libsass version to 0.15.0 fixes the issue for now.