Add error handling to scm_version.py script (#13521)

raise Exception in the case that return code is non-zero

this approach has shown itself to be the most consistently reliable across multiple ecosystems

tools/scripts/scm_version.py

@@ -1,7 +1,6 @@
 import os
 import sys
 import subprocess
-import traceback
 
 try:
     from setuptools_scm import get_version
@@ -9,8 +8,13 @@ except ModuleNotFoundError:
     sys.stderr.write("Unable to import setuptools-scm, attempting to install now...\n")
 
     os.environ['PIP_DISABLE_PIP_VERSION_CHECK'] = '1'
-    subprocess.check_output([sys.executable, '-m', 'ensurepip'])
-    subprocess.check_output([sys.executable, '-m', 'pip', 'install', 'setuptools-scm'])
+    COMMANDS = ([sys.executable, '-m', 'ensurepip'], [sys.executable, '-m', 'pip', 'install', 'setuptools-scm'])
+    for cmd in COMMANDS:
+        # capture_output because we only want to print version to stdout if successful
+        result = subprocess.run(cmd, capture_output=True)
+        if result.returncode:
+            # failed, we have no version, so print output so that users can debug
+            raise Exception(f'\nCommand `{" ".join(cmd)}` failed (rc={result.returncode}).\n\nstdout:\n{result.stdout}\n\nstderr:\n{result.stderr}')
 
     from setuptools_scm import get_version