Add `check-changes` rule for checking formatting of changes files.

Additional fixes to make the change work;
- fix Python 2 vs 3 issues
- fix some PEP 8 warnings
- handle paths with numbers correctly
- mention the make rule in doc/HACKING.

Makefile.am

@@ -111,6 +111,12 @@ check-logs:
 	./scripts/maint/checkLogs.pl                  \
 		src/*/*.[ch] | sort -n
 
+.PHONY: check-changes
+check-changes:
+	@if test -d "$(top_srcdir)/changes"; then \
+		$(PYTHON) $(top_srcdir)/scripts/maint/lintChanges.py $(top_srcdir)/changes/*; \
+		fi
+
 version:
 	@echo "Tor @VERSION@"
 	@if test -d "$(top_srcdir)/.git" && test -x "`which git 2>&1;true`"; then \

changes/feature15180

+  o Minor features (testing):
+    - Add make rule `check-changes` to verify the format of changes files.
+      Closes ticket 15180.

doc/HACKING

@@ -61,9 +61,10 @@ it's a bugfix, mention what bug it fixes and when the bug was
 introduced.  To find out which Git tag the change was introduced in,
 you can use "git describe --contains <sha1 of commit>".
 
-If at all possible, try to create this file in the same commit where
-you are making the change.  Please give it a distinctive name that no
-other branch will use for the lifetime of your change.
+If at all possible, try to create this file in the same commit where you are
+making the change.  Please give it a distinctive name that no other branch will
+use for the lifetime of your change. To verify the format of the changes file,
+you can use "make check-changes".
 
 When we go to make a release, we will concatenate all the entries
 in changes to make a draft changelog, and clear the directory. We'll

scripts/maint/lintChanges.py

 #!/usr/bin/python
 
+from __future__ import print_function
+from __future__ import with_statement
 import sys
 import re
-
+import os
 
 
 def lintfile(fname):
     have_warned = []
+
     def warn(s):
         if not have_warned:
             have_warned.append(1)
-            print fname,":"
-        print "\t",s
+            print("{}:".format(fname))
+        print("\t{}".format(s))
 
-    m = re.search(r'(\d{3,})', fname)
+    m = re.search(r'(\d{3,})', os.path.basename(fname))
     if m:
         bugnum = m.group(1)
     else:
@@ -23,7 +26,7 @@ def lintfile(fname):
         contents = f.read()
 
     if bugnum and bugnum not in contents:
-        warn("bug number %s does not appear"%bugnum)
+        warn("bug number {} does not appear".format(bugnum))
 
     lines = contents.split("\n")
     isBug = ("bug" in lines[0] or "fix" in lines[0])
@@ -44,11 +47,12 @@ def lintfile(fname):
     if re.search(r'[bB]ug (\d+)', contents):
         if not re.search(r'[Bb]ugfix on ', contents):
             warn("bugfix does not say 'bugfix on X.Y.Z'")
-        elif not re.search('[fF]ixes ([a-z ]*)bug (\d+); bugfix on ', contents):
+        elif not re.search('[fF]ixes ([a-z ]*)bug (\d+); bugfix on ',
+                           contents):
             warn("bugfix incant is not semicoloned")
 
 
-if __name__=='__main__':
+if __name__ == '__main__':
     for fname in sys.argv[1:]:
         if fname.endswith("~"):
             continue