Proposal for fix of #312 (#313)

* Proposal for fix of #312

This change moves the directory separator into the `PIPX_DIR` variable in order to not introduce an error in the case pipx has already been installed systemwide.

* Bump patch version of python feature to 1.0.16

src/python/devcontainer-feature.json

 {
   "id": "python",
-  "version": "1.0.15",
+  "version": "1.0.16",
   "name": "Python",
   "documentationURL": "https://github.com/devcontainers/features/tree/main/src/python",
   "description": "Installs the provided version of Python, as well as PIPX, and other common Python utilities.  JupyterLab is conditionally installed with the python feature. Note: May require source code compilation.",

src/python/install.sh

@@ -450,11 +450,11 @@ if [[ "${INSTALL_PYTHON_TOOLS}" = "true" ]] && [[ $(python --version) != "" ]];
     if ! type pipx > /dev/null 2>&1; then
         pip3 install --disable-pip-version-check --no-cache-dir --user pipx 2>&1
         /tmp/pip-tmp/bin/pipx install --pip-args=--no-cache-dir pipx
-        PIPX_DIR="/tmp/pip-tmp/bin"
+        PIPX_DIR="/tmp/pip-tmp/bin/"
     fi
     for util in "${DEFAULT_UTILS[@]}"; do
         if ! type ${util} > /dev/null 2>&1; then
-            "${PIPX_DIR}/pipx" install --system-site-packages --pip-args '--no-cache-dir --force-reinstall' ${util}
+            "${PIPX_DIR}pipx" install --system-site-packages --pip-args '--no-cache-dir --force-reinstall' ${util}
         else
             echo "${util} already installed. Skipping."
         fi