Use python -m venv instead of virtualenv command

https://github.com/sclorg/s2i-python-container/pull/374

Dockerfile

@@ -57,7 +57,7 @@ COPY ./root/ /
 # - In order to drop the root user, we have to make some directories world
 #   writable as OpenShift default security model is to run the container
 #   under random UID.
-RUN virtualenv ${APP_ROOT} && \
+RUN python3.8 -m venv ${APP_ROOT} && \
 chown -R 1001:0 ${APP_ROOT} && \
 fix-permissions ${APP_ROOT} -P
 

s2i/bin/assemble

@@ -9,13 +9,9 @@ function should_collectstatic() {
 }
 
 function virtualenv_bin() {
-  if head "/etc/redhat-release" | grep -q "^CentOS Linux release 7" || \
-     head "/etc/redhat-release" | grep -q "^Red Hat Enterprise Linux\( Server\)\? release 7" || \
-     head "/etc/redhat-release" | grep -q "^Fedora release"; then
-    virtualenv $1
-  else
-    virtualenv-${PYTHON_VERSION} $1
-  fi
+    # New versions of Python (>3.6) should use venv module
+    # from stdlib instead of virtualenv package
+    python3.8 -m venv $1
 }
 
 # Install pipenv to the separate virtualenv to isolate it