Small changes

.gitlab-ci.yml

@@ -140,7 +140,7 @@ minimal-sympy-master:
     - pip install git+https://gitlab-ci-token:${CI_JOB_TOKEN}@i10git.cs.fau.de/pycodegen/pystencils.git@master#egg=pystencils
     - python -m pip install --upgrade git+https://github.com/sympy/sympy.git
     - pip list
-    - python setup.py quicktest
+    - python quicktest.py
   allow_failure: true
   tags:
     - docker

setup.py

-from setuptools import setup
+from setuptools import setup, __version__ as setuptools_version
+
+if int(setuptools_version.split('.')[0]) < 61:
+    raise Exception(
+        "[ERROR] lbmpy requires at least setuptools version 61 to install.\n"
+        "If this error occurs during an installation via pip, it is likely that there is a conflict between "
+        "versions of setuptools installed by pip and the system package manager. "
+        "In this case, it is recommended to install lbmpy into a virtual environment instead."
+    )
+
 import versioneer