fix: do not require bleach module by default

Signed-off-by: Christopher Arndt <chris@chrisarndt.de>

README.md

@@ -70,6 +70,9 @@ steps:
     substtution is considered to be in Markdown format and will be rendered to
     HTML and sent as a formatted message with `org.matrix.custom.html` format.
 
+    Using this feature requires the `markdown` and `bleach` Python modules to
+    be available (the plugin's docker image has them installed).
+
 * `markdown_extensions` *(default:* `admonition, extra, sane_lists, smarty`)
 
     Comma-separated list of enabled Markdown extensions. See this
@@ -107,8 +110,8 @@ steps:
     ID of user on homeserver to send message as (ID, not username).
 
 
-[`DEFAULT_ALLOWED_ATTRS`]: ./matrixchat-notify.py#L29
-[`DEFAULT_ALLOWED_TAGS`]: ./matrixchat-notify.py#L35
+[`DEFAULT_ALLOWED_ATTRS`]: ./matrixchat-notify.py#L27
+[`DEFAULT_ALLOWED_TAGS`]: ./matrixchat-notify.py#L34
 [allowed attributes]: https://bleach.readthedocs.io/en/latest/clean.html#allowed-attributes-attributes
 [drone.io]: https://drone.io/
 [list of extensions]: https://python-markdown.github.io/extensions/

matrixchat-notify.py

@@ -20,36 +20,47 @@ from distutils.util import strtobool
 from os.path import exists
 from string import Template
 
-import bleach
 from nio import AsyncClient, LoginResponse
 
 PROG = "matrixchat-notify"
 CONFIG_FILENAME = f"{PROG}-config.json"
-DEFAULT_ALLOWED_ATTRS = bleach.ALLOWED_ATTRIBUTES.copy()
-DEFAULT_ALLOWED_ATTRS.update(
-    {
+DEFAULT_ALLOWED_ATTRS = {
     "*": ["class"],
+    "a": ["href", "title"],
+    "abbr": ["title"],
+    "acronym": ["title"],
     "img": ["alt", "src"],
 }
-)
-DEFAULT_ALLOWED_TAGS = bleach.ALLOWED_TAGS | {
+DEFAULT_ALLOWED_TAGS = {
+    "a",
+    "abbr",
+    "acronym",
+    "b",
+    "blockquote",
+    "code",
     "dd",
     "div",
     "dl",
     "dt",
+    "em",
     "h1",
     "h2",
     "h3",
     "h4",
     "h5",
     "h6",
+    "i",
+    "li",
+    "ol",
     "p",
     "span",
+    "strong",
     "table",
     "td",
     "th",
     "thead",
     "tr",
+    "ul",
 }
 DEFAULT_HOMESERVER = "https://matrix.org"
 DEFAULT_MARKDOWN_EXTENSIONS = "admonition, extra, sane_lists, smarty"
@@ -171,6 +182,7 @@ def render_message(config):
 
 
 def render_markdown(message, config):
+    import bleach
     import markdown
 
     allowed_attrs = config.get("allowed_attrs", DEFAULT_ALLOWED_ATTRS)