Make xbbtools imports work on Python 2 and 3
Use unittest methods instead of assert statement
Some my_dict.keys()  -->  list(my_dict.keys()) etc changes.

This is a harmless change under Python 2 (with a
small performace hit) but means the code does not
need alteration under Python 3.

These changes were suggested by the 2to3 dict fixer
but manually reviewed.
Replace .iteritems() with .iter() and .itervalues() with .values()

This makes the code work as-is on Python 3 without needing
the 2to3 dict fixer, which is good.

On the downside, it means using lists under Python 2 in some
situations where it would be more memory efficient not to.

Note I also checked there were no remaining uses of .iterkeys()
which is generally pointless as can iterate over a dict directly.

    import os
    import commands
    def clean(filename):
        with open(filename, "rU") as h:
            lines = list(h)
        fix = False
        for line in lines:
            if ".iterkeys()" in line:
                print(line)
                print(filename)
                import sys
                sys.exit(1)
            if ".iteritems()" in line \
            or ".iterkeys()" in line \
            or ".itervalues()" in line:
                fix = True
                break
        if not fix:
            return False
        with open(filename, "w") as h:
            for line in lines:
                line = line.replace(".iteritems()", ".items()")
                line = line.replace(".iterkeys()", ".keys()")
                line = line.replace(".itervalues()", ".values()")
                h.write(line)
        return True

    good = 0
    bad = 0
    bad_list = open("iter_2to3.txt", "w")
    for dirpath, dirnames, filenames in os.walk("."):
        if dirpath.startswith("./build"):
            continue
        if dirpath == "." or dirpath.startswith("./Bio/_py3k"):
            continue
        for f in sorted(filenames):
            if not f.endswith(".py"):
                continue
            if f == "run_tests.py" or f == "_six.py":
                continue
            py2filename = os.path.join(dirpath, f)
            if clean(py2filename):
                bad += 1
                print(py2filename)
                bad_list.write("%s\n" % py2filename)
                os.system("git add %s" % py2filename)
            else:
                good += 1
    bad_list.close()
    print("%i no change, %i need fixers" % (good, bad))
    print("Troublesome ones %0.1f%%" % ((bad*100.0)/(good+bad)))

Conflicts:

	Bio/Data/CodonTable.py
	Bio/SeqUtils/__init__.py
Use Python 3 like dictionary as model for indexing files
No longer need the 2to3 dict fixer (according to unit tests)

Scanning the remaining changes suggested by 2to3 -f dict by
eye they are probably all false positives (e.g. adding
list(...) where a dictionary method is used in a iterator).

Any issues with list vs iterator problems uncovered shouldn't
just be fixed without also expanding the unit test coverage.
Fix for editing dictionary while iterating over it