Add an all-python test script.

This uses Tim Peters's ndiff to produce nice diffs without invoking an
external program.

lib/python/TAL/runtest.py

+# runtest.py
+
+import sys
+import os
+import string
+from cStringIO import StringIO
+import glob
+
+import driver
+
+def showdiff(a, b):
+    import ndiff
+    cruncher = ndiff.SequenceMatcher(ndiff.IS_LINE_JUNK, a, b)
+    for tag, alo, ahi, blo, bhi in cruncher.get_opcodes():
+        if tag == 'replace':
+            print nicerange(alo, ahi) + "r" + nicerange(blo, bhi)
+            ndiff.dump('<', a, alo, ahi)
+            print "---"
+            ndiff.dump('>', b, blo, bhi)
+        elif tag == 'delete':
+            print nicerange(alo, ahi) + "d" + nicerange(blo, bhi)
+            ndiff.dump('<', a, alo, ahi)
+        elif tag == 'insert':
+            print nicerange(alo, ahi), "i", nicerange(blo, bhi)
+            ndiff.dump('>', b, blo, bhi)
+        elif tag == 'equal':
+            pass
+        else:
+            raise ValueError, 'unknown tag ' + `tag`
+
+def nicerange(lo, hi):
+    if hi <= lo+1:
+        return str(lo+1)
+    else:
+        return "%d,%d" % (lo+1, hi)
+
+def main():
+    opts = []
+    args = sys.argv[1:]
+    while args and args[0][:1] == '-':
+        opts.append(args[0])
+        del args[0]
+    if not args:
+        args = glob.glob(os.path.join("test", "test*.xml"))
+    for arg in args:
+        print
+        print arg,
+        sys.stdout.flush()
+        save = sys.stdout, sys.argv
+        try:
+            sys.stdout = stdout = StringIO()
+            sys.argv = [""] + opts + [arg]
+            driver.main()
+        finally:
+            sys.stdout, sys.argv = save
+        head, tail = os.path.split(arg)
+        outfile = os.path.join(
+            head,
+            string.replace(tail, "test", "out"))
+        try:
+            f = open(outfile)
+        except IOError:
+            expected = None
+        else:
+            expected = f.readlines()
+            f.close()
+        stdout.seek(0)
+        actual = stdout.readlines()
+        if actual == expected:
+            print "OK"
+        else:
+            print "not OK"
+            showdiff(expected, actual)
+
+if __name__ == "__main__":
+    main()