INSTALL: detecting if the venv is outdated to support better python v…

…ersion upgrades (usually through OS upgrades)

install.sh

@@ -196,21 +196,37 @@ fi
 cd ${root_dir}
 if [ -x "$(command -v python3.9)" ] ; then
   python=python3.9
-  if [ ! -d "venv" ]; then
-    echo "Creating Python 3.9 virtual environment"
-    ${python} -m venv venv
-  fi
+  pyvers="3.9"
 elif [ -x "$(command -v python3.7)" ] ; then
   python=python3.7
-  if [ ! -d "venv" ]; then
-    echo "Creating Python 3.7 virtual environment"
-    ${python} -m venv venv
-  fi
+  pyvers="3.7"
 else
   echo "Please install Python 3.7 or 3.9 (you might need to upgrade your Linux distribution)"
   exit 1
 fi
 
+# Common venv management code
+if [ ! -d "venv" ]; then
+  echo "Creating Python ${pyvers} virtual environment"
+  ${python} -m venv venv
+else
+  # Checking which version of python was used to create the existing venv
+  if [ -e "venv/bin/python3.9" ]; then
+    venv_vers=python3.9
+  elif [ -e "venv/bin/python3.7" ]; then
+    venv_vers=python3.7
+  else
+    # Attempting a blind detection of whatever unexpected version there could be
+    venv_vers=$(ls -1 venv/bin/python3.?)
+  fi
+
+  if [ "${venv_vers}" != "${python}" ]; then
+    echo "Replacing Python ${venv_vers} virtual environment with version ${pyvers}"
+    rm -fr venv
+    ${python} -m venv venv
+  fi
+fi
+
 echo "Installing PyPi requirements"
 if [ $upgrade -eq 1 ]; then
   echo "Updating Python requirements - 7/14" > /tmp/pynab.upgrade