breaking change, drop support for setuptools<12

setuptools_scm/__main__.py

@@ -4,9 +4,14 @@
 from setuptools_scm.integration import find_files
 from setuptools_scm.version import _warn_if_setuptools_outdated
 
-if __name__ == '__main__':
+
+def main():
     _warn_if_setuptools_outdated()
     print('Guessed Version', get_version())
     if 'ls' in sys.argv:
         for fname in find_files('.'):
             print(fname)
+
+
+if __name__ == '__main__':
+    main()

setuptools_scm/version.py

@@ -6,7 +6,6 @@
 
 from pkg_resources import iter_entry_points
 
-from distutils import log
 from pkg_resources import parse_version
 
 
@@ -21,10 +20,17 @@ def _get_version_class():
 VERSION_CLASS = _get_version_class()
 
 
+class SetuptoolsOutdatedWarning(Warning):
+    pass
+
+
+# append so integrators can disable the warning
+warnings.simplefilter('error', SetuptoolsOutdatedWarning, append=1)
+
+
 def _warn_if_setuptools_outdated():
     if VERSION_CLASS is None:
-        log.warn("your setuptools is too old (<12)")
-        log.warn("setuptools_scm functionality is degraded")
+        warnings.warn("your setuptools is too old (<12)", SetuptoolsOutdatedWarning)
 
 
 def callable_or_entrypoint(group, callable_or_name):

testing/test_setuptools_support.py

@@ -0,0 +1,60 @@
+"""
+integration tests that check setuptools version support
+"""
+import sys
+import os
+import subprocess
+import pytest
+pytestmark = pytest.mark.skipif(
+    "sys.version_info >= (3,6,0)",
+    reason="integration with old versions no longer needed on py3.6+")
+
+
+@pytest.fixture(scope='session')
+def get_setuptools_packagedir(request):
+    targets = request.config.cache.makedir('setuptools_installs')
+
+    def makeinstall(version):
+        target = targets.ensure(version, dir=1)
+        subprocess.check_call([
+            sys.executable, '-m', 'pip',
+            'install', '--no-binary', 'setuptools', 'setuptools==' + version,
+            '-t', str(target),
+        ])
+        return target
+    return makeinstall
+
+
+SCRIPT = """
+import setuptools
+print(setuptools.__version__)
+import setuptools_scm.version
+from setuptools_scm.__main__ import main
+main()
+"""
+
+
+def check(packagedir, **env):
+    subprocess.check_call(
+        [sys.executable, '-c', SCRIPT],
+        env=dict(os.environ, PYTHONPATH=".:" + str(packagedir), **env))
+
+
+def test_old_setuptools_fails(get_setuptools_packagedir):
+    packagedir = get_setuptools_packagedir("0.9.8")
+    with pytest.raises(subprocess.CalledProcessError):
+        check(packagedir)
+
+
+def test_old_setuptools_allows_with_warnings(get_setuptools_packagedir):
+
+    packagedir = get_setuptools_packagedir("0.9.8")
+    # filter using warning since in the early python startup
+    check(
+        packagedir,
+        PYTHONWARNINGS="once::Warning")
+
+
+def test_distlib_setuptools_works(get_setuptools_packagedir):
+    packagedir = get_setuptools_packagedir("12.0.1")
+    check(packagedir)