Skip test if adios2 python module built without MPI. (#3124)

* This test only works if ADIOS2 was built with MPI.

* Require MPI ADIOS2 build during configuration.

* Reformat ruff.

* Require adios2.10 for given test

* Ruff

* Simplify

* Add back skip

---------

Co-authored-by: Garth N. Wells <gnw20@cam.ac.uk>
Co-authored-by: jorgensd <dokken92@gmail.com>
Co-authored-by: Jørgen S. Dokken <dokken@simula.no>

python/test/unit/io/test_adios2.py

@@ -293,7 +293,9 @@ def test_vtx_reuse_mesh(self, tempdir, dim, simplex, reuse):
         """Test reusage of mesh by VTXWriter."""
         from dolfinx.io import VTXMeshPolicy, VTXWriter
 
-        adios2 = pytest.importorskip("adios2")
+        adios2 = pytest.importorskip("adios2", minversion="2.10.0")
+        if not adios2.is_built_with_mpi:
+            pytest.skip("Require adios2 built with MPI support")
 
         mesh = generate_mesh(dim, simplex)
         v = Function(functionspace(mesh, ("Lagrange", 1)))
@@ -312,19 +314,12 @@ def test_vtx_reuse_mesh(self, tempdir, dim, simplex, reuse):
 
         reuse_variables = ["NumberOfEntities", "NumberOfNodes", "connectivity", "geometry", "types"]
         target_all = 3  # For all other variables the step count is number of writes
-        target_mesh = (
-            1 if reuse else 3
-        )  # For mesh variables the step count is 1 if reuse else number of writes
-
-        # backwards compatibility adios2 < 2.10.0
-        try:
-            adios_file = adios2.open(str(filename), "r", comm=mesh.comm, engine_type="BP4")
-        except AttributeError:
-            # adios2 >= v2.10.0
-            adios = adios2.Adios(comm=mesh.comm)
-            io = adios.declare_io("TestData")
-            io.set_engine("BP4")
-            adios_file = adios2.Stream(io, str(filename), "r", mesh.comm)
+        target_mesh = 1 if reuse else 3
+        # For mesh variables the step count is 1 if reuse else number of writes
+        adios = adios2.Adios(comm=mesh.comm)
+        io = adios.declare_io("TestData")
+        io.set_engine("BP4")
+        adios_file = adios2.Stream(io, str(filename), "r", mesh.comm)
 
         for name, var in adios_file.available_variables().items():
             if name in reuse_variables: