First draft of script to verify links in Markdown file work

The goal of this script is to go through a Markdown file and verify
the links all work.  Currently, only relative path links to files in
the same directory are tested.

verify-markdown-links.py

@@ -0,0 +1,50 @@
+#!/usr/bin/python3
+# Copyright © 2021, Bradley M. Kuhn
+#  Also copyrighted by others as well (no notices shared), and it is 
+# Licensed CC-BY-SA-4.0 because I borrowed an example from: https://www.py4u.net/discuss/208440
+import sys
+import re
+from pathlib import Path
+    
+INLINE_LINK_RE = re.compile(r'\[([^\]]+)\]\(([^)]+)\)')
+FOOTNOTE_LINK_TEXT_RE = re.compile(r'\[([^\]]+)\]\[(\d+)\]')
+FOOTNOTE_LINK_URL_RE = re.compile(r'\[(\d+)\]:\s+(\S+)')
+
+
+def find_md_links(md):
+    """ Return dict of links in markdown """
+
+    links = list(INLINE_LINK_RE.findall(md))
+    footnote_links = dict(FOOTNOTE_LINK_TEXT_RE.findall(md))
+    footnote_urls = dict(FOOTNOTE_LINK_URL_RE.findall(md))
+
+    for key in footnote_links.keys():
+        links.append((footnote_links[key], footnote_urls[footnote_links[key]]))
+
+    return links
+
+body_markdown =  sys.stdin.read()
+
+for (text, link) in find_md_links(body_markdown):
+    errMsg = None
+    if not re.match(r'^(mailto|http|ftp|#)', link, re.IGNORECASE):
+        path = Path(link)
+        if not path.is_file():
+            errMsg = "local file by that name does not exist for relative file link"
+    # FIXME: test other types of links
+    if errMsg:
+        print("Bad link of \"%s\" (labeled as \"%s\") has error: %s" % (link, text, errMsg))
+
+exit(0)
+# Below doesn't work, didn't have time to find out why
+
+
+import markdown
+from lxml import etree
+import sys
+
+body_markdown =  sys.stdin.read()
+print(markdown.markdown(body_markdown))
+doc = etree.fromstring(body)
+for link in doc.xpath('//a'):
+  print(link.text, link.get('href'))