Check that used Ansible can see Kolla Ansible

Fix-feature following up on the original check [1] to make it
test the correct interpreter.

Additionally, this change removes last, unneeded call to
random python - getting script directory is perfectly
doable in bash.

All checks are done from Python, not Ansible, due to its
performance. Python version feels snappy (0.2 s to check),
compared to sluggish Ansible (2.0 s to check).
What is more, relying on Ansible would require hacky solutions
to e.g. prevent custom config from interfering with it.
We might be willing to steer Ansible from Python in the future
anyhow.

[1] Icf0399d21b3fde8d530d73e6e7ee4a57665da276

Change-Id: Ib8f2e6b6672e7c06aa94bc226c4d72640d25d8c2
Closes-Bug: #1856346

releasenotes/notes/bug-1856346-59d0f01005d56e81.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    Kolla Ansible checks now that the local Ansible Python environment
+    is coherent, i.e. used Ansible can see Kolla Ansible.
+    `LP#1856346 <https://launchpad.net/bugs/1856346>`__

tools/kolla-ansible

@@ -2,21 +2,71 @@
 #
 # This script can be used to interact with kolla via ansible.
 
-function check_ansible_compatibility {
-    ANSIBLE_VERSION_MIN=2.8
-    ANSIBLE_VERSION_MAX=2.9
-    ANSIBLE_VERSION_HOST=$(ANSIBLE_DEBUG=0 ansible --version | head -n1 | egrep -o '[0-9]\.[0-9]+')
+function check_environment_coherence {
+    local ansible_path
+    ansible_path=$(which ansible)
 
-    if [[ $(printf "%s\n" "$ANSIBLE_VERSION_MIN" "$ANSIBLE_VERSION_MAX" "$ANSIBLE_VERSION_HOST" | sort -V | head -n1) != "$ANSIBLE_VERSION_MIN" ]] ||
-       [[ $(printf "%s\n" "$ANSIBLE_VERSION_MIN" "$ANSIBLE_VERSION_MAX" "$ANSIBLE_VERSION_HOST" | sort -V | tail -1)  != "$ANSIBLE_VERSION_MAX" ]]; then
+    if [[ $? -ne 0 ]]; then
+        echo "ERROR: Ansible is not installed in the current (virtual) environment." >&2
+        exit 1
+    fi
+
+    local ansible_shebang_line
+    ansible_shebang_line=$(head -n1 "$ansible_path")
+
+    if ! echo "$ansible_shebang_line" | egrep "^#!" &>/dev/null; then
+        echo "ERROR: Ansible script is malformed (missing shebang line)." >&2
+        exit 1
+    fi
+
+    local ansible_python_cmdline
+    # NOTE(yoctozepto): may have multiple parts
+    ansible_python_cmdline=${ansible_shebang_line#\#\!}
+
+    if ! $ansible_python_cmdline --version &>/dev/null; then
+        echo "ERROR: Ansible Python is not functional." >&2
+        echo "Tried '$ansible_python_cmdline'" >&2
+        exit 1
+    fi
+
+    # Check for existence of kolla_ansible module using Ansible's Python.
+    if ! $ansible_python_cmdline -c 'import kolla_ansible' &>/dev/null; then
+        echo "ERROR: kolla_ansible has to be available in the Ansible PYTHONPATH." >&2
+        echo "Please install both in the same (virtual) environment." >&2
+        exit 1
+    fi
+
+    local ansible_version_output
+    ansible_full_version=$($ansible_python_cmdline -c 'import ansible; print(ansible.__version__)')
+
+    if [[ $? -ne 0 ]]; then
+        echo "ERROR: Failed to obtain Ansible version:" >&2
+        echo "$ansible_full_version" >&2
+        exit 1
+    fi
+
+    local ansible_version
+    ansible_version=$(echo "$ansible_full_version" | egrep -o '^[0-9]+\.[0-9]+')
+
+    if [[ $? -ne 0 ]]; then
+        echo "ERROR: Failed to parse Ansible version:" >&2
+        echo "$ansible_full_version" >&2
+        exit 1
+    fi
+
+    local ANSIBLE_VERSION_MIN=2.8
+    local ANSIBLE_VERSION_MAX=2.9
+
+    if [[ $(printf "%s\n" "$ANSIBLE_VERSION_MIN" "$ANSIBLE_VERSION_MAX" "$ansible_version" | sort -V | head -n1) != "$ANSIBLE_VERSION_MIN" ]] ||
+       [[ $(printf "%s\n" "$ANSIBLE_VERSION_MIN" "$ANSIBLE_VERSION_MAX" "$ansible_version" | sort -V | tail -n1) != "$ANSIBLE_VERSION_MAX" ]]; then
         echo "ERROR: Ansible version should be between $ANSIBLE_VERSION_MIN and $ANSIBLE_VERSION_MAX. Current version is $ANSIBLE_VERSION_HOST which is not supported."
         exit 1
     fi
 }
 
 function find_base_dir {
-    local real_path=$(python3 -c "import os;print(os.path.realpath('$0'))")
-    local dir_name="$(dirname "$real_path")"
+    local dir_name
+    dir_name=$(cd "$(dirname "$0")" &>/dev/null && pwd)
     if [ -z "$SNAP" ]; then
         if [[ ${dir_name} == "/usr/bin" ]]; then
             BASEDIR=/usr/share/kolla-ansible
@@ -131,7 +181,7 @@ prune-images
 EOF
 }
 
-check_ansible_compatibility
+check_environment_coherence
 
 SHORT_OPTS="hi:p:t:k:e:v"
 LONG_OPTS="help,inventory:,playbook:,skip-tags:,tags:,key:,extra:,verbose,configdir:,passwords:,limit:,forks:,vault-id:,ask-vault-pass,vault-password-file:,yes-i-really-really-mean-it,include-images,include-dev:,full,incremental"
@@ -139,12 +189,6 @@ LONG_OPTS="help,inventory:,playbook:,skip-tags:,tags:,key:,extra:,verbose,config
 RAW_ARGS="$*"
 ARGS=$(getopt -o "${SHORT_OPTS}" -l "${LONG_OPTS}" --name "$0" -- "$@") || { usage >&2; exit 2; }
 
-# Check for existence of kolla_ansible module using python3 interpreter.
-if ! python3 -c 'import kolla_ansible' &>/dev/null; then
-    echo "ERROR: kolla_ansible has to be available in the PYTHONPATH (e.g. installed)" >&2
-    exit 1
-fi
-
 eval set -- "$ARGS"
 
 find_base_dir