New component: Python Script (#7950)

* Add initial version

* Fix requirements

* Prefer logging over printing

* Set executor thread name on >Py36 only

* Add tests

* Lint

* Add restrictedpython to test dependencies

* Create python_script.py

From doc:
```
However, an empty dict ({}) is treated as is. If you want to specify a list that can contain anything, specify it as dict:
>>> schema = Schema({}, extra=ALLOW_EXTRA)  # don't do this
>>> try:
...   schema({'extra': 1})
...   raise AssertionError('MultipleInvalid not raised')
... except MultipleInvalid as e:
...   exc = e
>>> str(exc) == "not a valid value"
True
>>> schema({})
{}
>>> schema = Schema(dict)  # do this instead
>>> schema({})
{}
>>> schema({'extra': 1})
{'extra': 1}

```

homeassistant/components/python_script.py

@@ -0,0 +1,86 @@
+"""Component to allow running Python scripts."""
+import glob
+import os
+import logging
+
+import voluptuous as vol
+
+DOMAIN = 'python_script'
+REQUIREMENTS = ['restrictedpython==4.0a2']
+FOLDER = 'python_scripts'
+_LOGGER = logging.getLogger(__name__)
+
+CONFIG_SCHEMA = vol.Schema({
+    DOMAIN: vol.Schema(dict)
+}, extra=vol.ALLOW_EXTRA)
+
+
+def setup(hass, config):
+    """Initialize the python_script component."""
+    path = hass.config.path(FOLDER)
+
+    if not os.path.isdir(path):
+        _LOGGER.warning('Folder %s not found in config folder', FOLDER)
+        return False
+
+    def service_handler(call):
+        """Handle python script service calls."""
+        filename = '{}.py'.format(call.service)
+        with open(hass.config.path(FOLDER, filename)) as fil:
+            execute(hass, filename, fil.read(), call.data)
+
+    for fil in glob.iglob(os.path.join(path, '*.py')):
+        name = os.path.splitext(os.path.basename(fil))[0]
+        hass.services.register(DOMAIN, name, service_handler)
+
+    return True
+
+
+def execute(hass, filename, source, data):
+    """Execute a script."""
+    from RestrictedPython import compile_restricted_exec
+    from RestrictedPython.Guards import safe_builtins, full_write_guard
+
+    compiled = compile_restricted_exec(source, filename=filename)
+
+    if compiled.errors:
+        _LOGGER.error('Error loading script %s: %s', filename,
+                      ', '.join(compiled.errors))
+        return
+
+    if compiled.warnings:
+        _LOGGER.warning('Warning loading script %s: %s', filename,
+                        ', '.join(compiled.warnings))
+
+    restricted_globals = {
+        '__builtins__': safe_builtins,
+        '_print_': StubPrinter,
+        '_getattr_': getattr,
+        '_write_': full_write_guard,
+    }
+    local = {
+        'hass': hass,
+        'data': data,
+        'logger': logging.getLogger('{}.{}'.format(__name__, filename))
+    }
+
+    try:
+        _LOGGER.info('Executing %s: %s', filename, data)
+        # pylint: disable=exec-used
+        exec(compiled.code, restricted_globals, local)
+    except Exception as err:  # pylint: disable=broad-except
+        _LOGGER.exception('Error executing script %s: %s', filename, err)
+
+
+class StubPrinter:
+    """Class to handle printing inside scripts."""
+
+    def __init__(self, _getattr_):
+        """Initialize our printer."""
+        pass
+
+    def _call_print(self, *objects, **kwargs):
+        """Print text."""
+        # pylint: disable=no-self-use
+        _LOGGER.warning(
+            "Don't use print() inside scripts. Use logger.info() instead.")