Add null installer, integration tests for install/run

Fixes #438.

letsencrypt/plugins/null.py

@@ -0,0 +1,57 @@
+"""Null plugin."""
+import logging
+
+import zope.component
+import zope.interface
+
+from letsencrypt import interfaces
+from letsencrypt.plugins import common
+
+
+logger = logging.getLogger(__name__)
+
+
+class Installer(common.Plugin):
+    """Null installer."""
+    zope.interface.implements(interfaces.IInstaller)
+    zope.interface.classProvides(interfaces.IPluginFactory)
+
+    description = "Null Installer"
+
+    # pylint: disable=missing-docstring,no-self-use
+
+    def prepare(self):
+        pass  # pragma: no cover
+
+    def more_info(self):
+        return "Installer that doesn't do anything (for testing)."
+
+    def get_all_names(self):
+        return []
+
+    def deploy_cert(self, domain, cert_path, key_path, chain_path=None):
+        pass  # pragma: no cover
+
+    def enhance(self, domain, enhancement, options=None):
+        pass  # pragma: no cover
+
+    def supported_enhancements(self):
+        return []
+
+    def get_all_certs_keys(self):
+        return []
+
+    def save(self, title=None, temporary=False):
+        pass  # pragma: no cover
+
+    def rollback_checkpoints(self, rollback=1):
+        pass  # pragma: no cover
+
+    def view_config_changes(self):
+        pass  # pragma: no cover
+
+    def config_test(self):
+        pass  # pragma: no cover
+
+    def restart(self):
+        pass  # pragma: no cover