Fixing KeyError when banner main ref fails.

If banner main ref exists but fails during pre-build (which then gets
removed) an unhandled exception would be raised. Handling this by
checking before and after pre_build() if banner main ref exists.

Fixes #27

README.rst

@@ -56,7 +56,9 @@ Added
     * Time value of ``html_last_updated_fmt`` will be the last git commit (authored) date.
 
 Fixed
+    * Unhandled KeyError exception when banner main ref fails pre-build.
     * https://github.com/Robpol86/sphinxcontrib-versioning/issues/26
+    * https://github.com/Robpol86/sphinxcontrib-versioning/issues/27
 
 2.2.0 - 2016-09-15
 ------------------

sphinxcontrib/versioning/__main__.py

@@ -302,6 +302,10 @@ def build(config, rel_source, destination, **options):
     # Pre-build.
     log.info("Pre-running Sphinx to collect versions' master_doc and other info.")
     exported_root = pre_build(config.git_root, versions)
+    if config.banner_main_ref and config.banner_main_ref not in [r['name'] for r in versions.remotes]:
+        log.warning('Banner main ref %s failed during pre-run. Disabling banner.', config.banner_main_ref)
+        config.update(dict(banner_greatest_tag=False, banner_main_ref=None, banner_recent_tag=False, show_banner=False),
+                      overwrite=True)
 
     # Build.
     build_all(exported_root, destination, versions)

tests/test__main__/test_main_build_scenarios.py

@@ -671,3 +671,26 @@ def test_error_bad_root_ref(tmpdir, local_docs):
     with pytest.raises(CalledProcessError) as exc:
         pytest.run(local_docs, ['sphinx-versioning', '-N', '-v', 'build', '.', str(tmpdir), '-r', 'unknown'])
     assert 'Root ref unknown not found in: master' in exc.value.output
+
+
+def test_bad_banner(banner, local_docs):
+    """Test bad banner main ref.
+
+    :param banner: conftest fixture.
+    :param local_docs: conftest fixture.
+    """
+    pytest.run(local_docs, ['git', 'checkout', '-b', 'stable', 'master'])
+    local_docs.join('conf.py').write('bad\n', mode='a')
+    pytest.run(local_docs, ['git', 'commit', '-am', 'Breaking stable.'])
+    pytest.run(local_docs, ['git', 'push', 'origin', 'stable'])
+
+    # Run.
+    destination = local_docs.ensure_dir('..', 'destination')
+    args = ['--show-banner', '--banner-main-ref', 'stable']
+    output = pytest.run(local_docs, ['sphinx-versioning', 'build', '.', str(destination)] + args)
+    assert 'KeyError' not in output
+
+    # Check no banner.
+    assert 'Banner main ref is: stable' in output
+    assert 'Banner main ref stable failed during pre-run.' in output
+    banner(destination.join('contents.html'), None)