Freezing setuptools due to its incorrect operation

See (https://github.com/pypa/setuptools/issues/2350)

cli/setup.py

@@ -259,7 +259,7 @@ def gen_version():
         install_requires=_find_requirements(),
         package_data={'': _find_data_files('tessia')},
         packages=find_packages(exclude=['tests', 'tests.*']),
-        setup_requires=['setuptools>=30.3.0'],
+        setup_requires=['setuptools==49.6.0'],
         url=URL,
         version=gen_version(),
         zip_safe=False,

setup.py

@@ -246,7 +246,7 @@ def gen_version():
         install_requires=_find_requirements(),
         package_data={'': _find_data_files('tessia')},
         packages=find_packages(exclude=['tests', 'tests.*']),
-        setup_requires=['setuptools>=30.3.0'],
+        setup_requires=['setuptools==49.6.0'],
         url=URL,
         version=gen_version(),
         zip_safe=False,

tools/ci/docker/tessia-cli/Dockerfile

@@ -28,7 +28,7 @@ RUN apt-get -q update > /dev/null && \
     locale-gen en_US.UTF-8 && \
     update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 && \
     # set up python packaging tools
-    pip3 -q install -U setuptools pip && \
+    pip3 -q install -U "setuptools==49.6.0" pip && \
     # remove pip from distro to avoid conflicts
     apt-get -y remove python3-pip && hash -r && \
     # add the admin user for administrative work

tools/ci/docker/tessia-server/Dockerfile

@@ -47,7 +47,7 @@ RUN apt-get -q update > /dev/null && \
     locale-gen en_US.UTF-8 && \
     update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 && \
     # set up python packaging tools
-    pip3 -q install -U setuptools pip && \
+    pip3 -q install -U "setuptools==49.6.0" pip && \
     # remove pip from distro to avoid conflicts
     apt-get -y remove python3-pip && hash -r && \
     # web server for api service