Fix `extra_requires`
In two different local environemnts, and the CI, the command `pip install -e .[opt]` results in `WARNING: mala 0.2.0 does not provide the extra 'opt'`. I am unsure why. The most recent setuptools version this was tested with is 59.5.0 (because the current torch version breaks with versions higher then that). 

Comment by @DanielKotik:
Once this is fixed we need to make the approbriate changes in
```yml
# cpu-tests.yml
- name: Install mala package
  # ...
  run: |
     # ...
     # install extra dependencies
     pip install oapackage  # change to → pip install -e .[opt]
     pip install pytest     # change to → pip install -e .[test]
```
This then would also serve as a test indirectly.
diff --git a/.github/workflows/cpu-tests.yml b/.github/workflows/cpu-tests.yml
index dab0afb6..bceaae50 100644
--- a/.github/workflows/cpu-tests.yml
+++ b/.github/workflows/cpu-tests.yml
@@ -78,6 +78,7 @@ jobs:
       - name: Install mala package
         run: |
           pip --no-cache-dir install -e .
+          pip install oapackage==2.6.8
           pip install pytest
       - name: Check out repository (data)
         uses: actions/checkout@v2
diff --git a/install/mala_cpu_environment.yml b/install/mala_cpu_environment.yml
index f50b5630..730fbeb5 100644
--- a/install/mala_cpu_environment.yml
+++ b/install/mala_cpu_environment.yml
@@ -94,7 +94,7 @@ dependencies:
   - pyyaml=6.0=py38h497a2fe_3
   - readline=8.1=h46c0cb4_0
   - scipy=1.8.0=py38h56a6a73_0
-  - setuptools=60.8.1=py38h578d9bd_0
+  - setuptools=59.5.0=py38h578d9bd_0
   - six=1.16.0=pyh6c4a22f_0
   - sleef=3.5.1=h9b69904_2
   - sqlalchemy=1.4.31=py38h497a2fe_0
diff --git a/test/hyperopt_test.py b/test/hyperopt_test.py
index b00729cd..2fa66a74 100644
--- a/test/hyperopt_test.py
+++ b/test/hyperopt_test.py
@@ -84,8 +84,6 @@ class TestHyperparameterOptimization:
                max(performed_trials_values)
 
     def test_different_ho_methods(self):
-        import torch
-        print(torch.__version__)
         results = [self.__optimize_hyperparameters("optuna"),
                    self.__optimize_hyperparameters("oat"),
                    self.__optimize_hyperparameters("naswot")]
['test/hyperopt_test.py', 'install/mala_cpu_environment.yml', '.github/workflows/cpu-tests.yml']