make tox env for code-checks

This executes: check-debugging, check-interfaces, check-miscaptures,
find-trailing-spaces, check-umids, pyflakes.

Other changes:

* fix check-umids.py to take starting points. run it as `check-umids.py
  src` instead of `check-umids.py src/allmydata/*.py`
* check-debugging: rewrite in python to run from tox: tox doesn't like
  to run shell scripts.
* put check-interfaces.py last: it produces lots of warnings, but passes
  anyways. The others only produce significant output if they fail.

misc/coding_tools/check-umids.py

@@ -1,27 +1,29 @@
 #! /usr/bin/python
 
-# ./rumid.py foo.py
+# ./check-umids.py src
 
 import sys, re, os
 
 ok = True
 umids = {}
 
-for fn in sys.argv[1:]:
-    fn = os.path.abspath(fn)
-    for lineno,line in enumerate(open(fn, "r").readlines()):
-        lineno = lineno+1
-        if "umid" not in line:
-            continue
-        mo = re.search("umid=[\"\']([^\"\']+)[\"\']", line)
-        if mo:
-            umid = mo.group(1)
-            if umid in umids:
-                oldfn, oldlineno = umids[umid]
-                print "%s:%d: duplicate umid '%s'" % (fn, lineno, umid)
-                print "%s:%d: first used here" % (oldfn, oldlineno)
-                ok = False
-            umids[umid] = (fn,lineno)
+for starting_point in sys.argv[1:]:
+    for root, dirs, files in os.walk(starting_point):
+        for fn in [f for f in files if f.endswith(".py")]:
+            fn = os.path.join(root, fn)
+            for lineno,line in enumerate(open(fn, "r").readlines()):
+                lineno = lineno+1
+                if "umid" not in line:
+                    continue
+                mo = re.search("umid=[\"\']([^\"\']+)[\"\']", line)
+                if mo:
+                    umid = mo.group(1)
+                    if umid in umids:
+                        oldfn, oldlineno = umids[umid]
+                        print "%s:%d: duplicate umid '%s'" % (fn, lineno, umid)
+                        print "%s:%d: first used here" % (oldfn, oldlineno)
+                        ok = False
+                    umids[umid] = (fn,lineno)
 
 if ok:
     print "all umids are unique"