scripts: west_commands: verify minimum cmake version

A recent developer experience study has pointed out that it's very
common for people to miss that the minimum cmake version required by
zephyr is higher than that which is commonly packaged by Linux
distributions.

Since this is a serious usability issue, it's worth adding extra
checking from zcmake.py to make sure that west commands which run
cmake always print a sensible error message if the cmake version used
is too old. Make that happen.

Signed-off-by: Marti Bolivar <marti.bolivar@nordicsemi.no>

scripts/requirements.txt

@@ -8,6 +8,7 @@ git-spindle==2.0
 gitlint
 intelhex
 junit2html
+packaging
 ply==3.10
 pyelftools==0.24
 pykwalify

scripts/west_commands/zcmake.py

@@ -16,6 +16,7 @@ import subprocess
 import shutil
 import sys
 
+import packaging.version
 from west import log
 from west.util import quote_sh_list
 
@@ -41,6 +42,8 @@ def run_cmake(args, cwd=None, capture_output=False, dry_run=False):
     cmake = shutil.which('cmake')
     if cmake is None and not dry_run:
         log.die('CMake is not installed or cannot be found; cannot build.')
+    _ensure_min_version(cmake, dry_run)
+
     cmd = [cmake] + args
     kwargs = dict()
     if capture_output:
@@ -260,3 +263,34 @@ class CMakeCache:
 
     def __iter__(self):
         return iter(self._entries.values())
+
+def _ensure_min_version(cmake, dry_run):
+    cmd = [cmake, '--version']
+    if dry_run:
+        log.inf('Dry run:', quote_sh_list(cmd))
+        return
+
+    try:
+        version_out = subprocess.check_output(cmd, stderr=subprocess.DEVNULL)
+    except subprocess.CalledProcessError as cpe:
+        log.die('cannot get cmake version:', str(cpe))
+    decoded = version_out.decode('utf-8')
+    lines = decoded.splitlines()
+    if not lines:
+        log.die('can\'t get cmake version: ' +
+                'unexpected "cmake --version" output:\n{}\n'.
+                format(decoded) +
+                'Please install CMake ' + _MIN_CMAKE_VERSION_STR +
+                ' or higher (https://cmake.org/download/).')
+    version = lines[0].split()[2]
+    if packaging.version.parse(version) < _MIN_CMAKE_VERSION:
+        log.die('cmake version', version,
+                'is less than minimum version {};'.
+                format(_MIN_CMAKE_VERSION_STR),
+                'please update your CMake (https://cmake.org/download/).')
+    else:
+        log.dbg('cmake version', version, 'is OK; minimum version is',
+                _MIN_CMAKE_VERSION_STR)
+
+_MIN_CMAKE_VERSION_STR = '3.13.1'
+_MIN_CMAKE_VERSION = packaging.version.parse(_MIN_CMAKE_VERSION_STR)