fix: guard import in tests

Author: beckermr

tests/conftest.py

@@ -4,7 +4,6 @@
 
 import pytest
 
-from conda_forge_feedstock_check_solvable.mamba_solver import mamba_solver_factory
 from conda_forge_feedstock_check_solvable.rattler_solver import rattler_solver_factory
 
 FEEDSTOCK_DIR = os.path.join(os.path.dirname(__file__), "test_feedstock")
@@ -40,6 +39,10 @@ def pytest_generate_tests(metafunc):
         factories = []
         for solver in solvers:
             if solver == "mamba":
+                from conda_forge_feedstock_check_solvable.mamba_solver import (
+                    mamba_solver_factory,
+                )
+
                 factories.append(mamba_solver_factory)
             elif solver == "rattler":
                 factories.append(rattler_solver_factory)