roles/homeassistant: Install in a virtualenv

Because the Home Assistant user's home directory is on `/var`, Python
packages installed in the "user site" do not get the correct SELinux
labels and thus run in the wrong domain.  This causes a lot of AVC
denials and other issues that prevent Home Assistant from working
correctly.

To resolve this issue, Home Assistant is now installed in a virtual
environment at `/usr/local/homeassistant`.  This directory is still
owned by the Home Assistant user, allowing Home Assistant to manage
packages installed there.  Since it is rooted under `/usr`, files are
labelled correctly and processes launched from executables there will
run in the correct domain.

roles/homeassistant/vars/armv7l.yml

@@ -0,0 +1,12 @@
+# These are required to build Python packages that do not have wheels
+# on pypi.org for armv7hl
+homeassistant_arch_system_deps:
+- gcc
+- gcc-c++
+- libffi-devel
+- libopenzwave-devel
+- libudev-devel
+- make
+- openssl-devel
+- python3-devel
+- which