Bugfix: CVS fetching (#29793)

#27021 broke fetching for CVS-based packages because:

- The mirror logic was using URL parsing to extract a path from the
  CVS repository location
- #27021 added sanity checks to enforce that strings passed to the
  URL parser were actually URLs

This replaces the call to "url_util.parse" with logic that is
customized for CVS. This implies that VCSFetchStrategy should
rename the "url_attr" attribute to something more generic, but
that should be handled separately.

lib/spack/spack/fetch_strategy.py

@@ -1104,8 +1104,13 @@ def mirror_id(self):
         if not (self.branch or self.date):
             # We need a branch or a date to make a checkout reproducible
             return None
-        repo_path = url_util.parse(self.url).path
-        result = os.path.sep.join(['cvs', repo_path])
+        # Special-case handling because this is not actually a URL
+        elements = self.url.split(':')
+        final = elements[-1]
+        elements = final.split('/')
+        # Everything before the first slash is a port number
+        elements = elements[1:]
+        result = os.path.sep.join(['cvs'] + elements)
         if self.branch:
             result += '%branch=' + self.branch
         if self.date: