teach plugins with dependencies to behave

assets/assets.py

@@ -20,9 +20,14 @@ import os
 import logging
 
 from pelican import signals
-from webassets import Environment
-from webassets.ext.jinja2 import AssetsExtension
+logger = logging.getLogger(__name__)
 
+try:
+    import webassets
+    from webassets import Environment
+    from webassets.ext.jinja2 import AssetsExtension
+except ImportError:
+    webassets = None
 
 def add_jinja2_ext(pelican):
     """Add Webassets to Jinja2 extensions in Pelican settings."""
@@ -41,13 +46,15 @@ def create_assets_env(generator):
         for item in generator.settings['ASSET_CONFIG']:
             generator.env.assets_environment.config[item[0]] = item[1]
 
-    logger = logging.getLogger(__name__)
     if logging.getLevelName(logger.getEffectiveLevel()) == "DEBUG":
         generator.env.assets_environment.debug = True
 
 
 def register():
     """Plugin registration."""
-
-    signals.initialized.connect(add_jinja2_ext)
-    signals.generator_init.connect(create_assets_env)
+    if webassets:
+        signals.initialized.connect(add_jinja2_ext)
+        signals.generator_init.connect(create_assets_env)
+    else:
+        logger.warning('`assets` failed to load dependency `webassets`.'
+                       '`assets` plugin not loaded.')

assets/test_assets.py

@@ -13,10 +13,6 @@ import subprocess
 from pelican import Pelican
 from pelican.settings import read_settings
 
-import pytest
-
-assets = pytest.importorskip("assets")
-
 CUR_DIR = os.path.dirname(__file__)
 THEME_DIR = os.path.join(CUR_DIR, 'test_data')
 CSS_REF = open(os.path.join(THEME_DIR, 'static', 'css',
@@ -62,10 +58,10 @@ class TestWebAssets(unittest.TestCase):
     """Base class for testing webassets."""
 
     def setUp(self, override=None):
-        
+        import assets
         self.temp_path = mkdtemp(prefix='pelicantests.')
         settings = {
-            'PATH': os.path.join(os.path.dirname(CUR_DIR), 'tests', 'content'),
+            'PATH': os.path.join(os.path.dirname(CUR_DIR), 'test_data', 'content'),
             'OUTPUT_PATH': self.temp_path,
             'PLUGINS': [assets],
             'THEME': THEME_DIR,