incorrect and/or precedence in marker evaluation

[LnL7]

The evaluation in poetry2nix doesn't take and/or precedence into account, which causes problems with more complex conditionals. Like conditional dependencies which propagate their marker resulting in multiple conditions. eg.

foo; python_version > "3.4"
bar; sys_platform == "win32"  # depends on foo

nix-repl> evalPep508 ''python_version > "3.4" or python_version > "3.4" and sys_platform == "win32"''
false
nix-repl> evalPep508 ''python_version > "3.4" and sys_platform == "win32" or python_version > "3.4"''
true

Compared to the packaging module.

In [1]: from packaging.markers import Marker
In [2]: Marker('python_version > "3.4" or python_version > "3.4" and sys_platform == "win32"').evaluate()
Out[2]: True
In [3]: Marker('python_version > "3.4" and sys_platform == "win32" or python_version > "3.4"').evaluate()
Out[3]: True

[adisbladis]

Closed in b7617a7