pipx: add testcase w/ env vars PIPX_xxxx (#5845)

* pipx: add testcase w/ env vars PIPX_xxxx

* add note to the docs about env vars

* add note to the docs about env vars

* Apply suggestions from code review

* Update plugins/modules/pipx.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update plugins/modules/pipx_info.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* break long lines into smaller ones

Co-authored-by: Felix Fontein <felix@fontein.de>

tests/integration/targets/pipx/tasks/main.yml

@@ -230,3 +230,30 @@
         that:
           - install_jupyter is changed
           - '"ipython" in install_jupyter.stdout'
+
+##############################################################################
+- name: ensure /opt/pipx
+  ansible.builtin.file:
+    path: /opt/pipx
+    state: directory
+    mode: 0755
+
+- name: install tox site-wide
+  community.general.pipx:
+    name: tox
+    state: latest
+  register: install_tox_sitewide
+  environment:
+    PIPX_HOME: /opt/pipx
+    PIPX_BIN_DIR: /usr/local/bin
+
+- name: stat /usr/local/bin/tox
+  ansible.builtin.stat:
+    path: /usr/local/bin/tox
+  register: usrlocaltox
+
+- name: check assertions
+  ansible.builtin.assert:
+    that:
+      - install_tox_sitewide is changed
+      - usrlocaltox.stat.exists