Add a TOR_DISABLE_PRACTRACKER envvar for use by folks who don't care

Fixes part of bug 30752

Makefile.am

@@ -369,7 +369,9 @@ endif
 
 check-best-practices:
 if USEPYTHON
-	$(PYTHON) $(top_srcdir)/scripts/maint/practracker/practracker.py $(top_srcdir)
+	@if test "$$TOR_DISABLE_PRACTRACKER" = ""; then \
+		$(PYTHON) $(top_srcdir)/scripts/maint/practracker/practracker.py $(top_srcdir); \
+	fi
 endif
 
 practracker-regen:

scripts/maint/practracker/practracker.py

@@ -227,6 +227,9 @@ Please fix the problems if you can, and update the exceptions file
 ({}) if you can't.
 
 See doc/HACKING/HelpfulTools.md for more information on using practracker.\
+
+You can disable this message by setting the TOR_DISABLE_PRACTRACKER environment
+variable.
 """.format(found_new_issues, exceptions_file)
         print(new_issues_str)