Flake8:

var/spack/repos/builtin/packages/votca-csg/package.py:30: [E231] missing whitespace after ','
var/spack/repos/builtin/packages/votca-ctp/package.py:28: [E231] missing whitespace after ','
var/spack/repos/builtin/packages/votca-ctp/package.py:29: [E231] missing whitespace after ','
var/spack/repos/builtin/packages/votca-xtp/package.py:29: [E231] missing whitespace after ','
var/spack/repos/builtin/packages/votca-xtp/package.py:30: [E231] missing whitespace after ','

sigh

I'll note that I don't consider this a concretizer bug and I think this change is the ideal way to resolve the problem: we intend that a when spec like [email protected] applies to 1.5 as well as 1.5.1 (in order to allow specifying @1.5 to mean all instances of 1.5.x). Given that, @1.5 is ambiguous when a package has both 1.5/1.5.1.

In other words, a package could legitimately request:

Foo()
  depends_on(x, [email protected])
  depends_on(y, [email protected])

In which case we want foo to depend on x and y when @1.5.1.

Avoiding this issue in the case of votca would be complicated: Spack would have to analyze the depends_on clauses to check whether x and y are conflicting and if the when_specs are simultaneously satisfiable; it would then have to further extrapolate that a user wouldn't actually request x and y together (in this case where x=[email protected] and y=[email protected]). To be clear I don't think even the new concretizer would attempt this: it just outputs whether the constraints are satisfiable and doesn't attempt an alternative interpretation of the constraints in the case that they aren't.

This brings me back to the discussion in #8957. In general, I agree, I should be able to say something like depends_on('[email protected]') and have Spack know I mean 3.7.X. I also wish there was an easier way to handle things like patch('foo.patch', when='@3.2') when a package contains 3.2 and 3.2.1. My first thought was to change the behavior depending on whether or not a package actually contains both 3.2 and 3.2.1, but I can see how that would make concretizer design a nightmare.