bpo-41748: Handles unquoted attributes with commas (#24072)

* bpo-41748: Adds tests for unquoted attributes with comma

* bpo-41748: Handles unquoted attributes with comma

* bpo-41748: Addresses review comments

* bpo-41748: Addresses review comments

* Adds more test cases
* Simplifies the regex for handling spaces

* bpo-41748: Moves attributes tests under the right class

* bpo-41748: Addresses review about duplicate attributes

* bpo-41748: Adds NEWS.d entry for this patch

Lib/html/parser.py

@@ -46,7 +46,7 @@ locatestarttagend_tolerant = re.compile(r"""
           |"[^"]*"                   # LIT-enclosed value
           |(?!['"])[^>\s]*           # bare value
          )
-         (?:\s*,)*                   # possibly followed by a comma
+        \s*                          # possibly followed by a space
        )?(?:\s|/(?!>))*
      )*
    )?