issue2551203 - Add support for CORS preflight request Add support for unauthenticated CORS preflight and fix headers for CORS. client.py: pass through unauthenticated CORS preflight to rest backend. Normal rest OPTION handlers (including tracker defined extensions) can see and handle the request. make some error cases return error json with crrect mime type rather than plain text tracebacks. create new functions to verify origin and referer that filter using allowed origins setting. remove tracker base url from error message is referer is not at an allowed origin. rest.py: fix up OPTION methods handlers to include Access-Control-Allow-Methods that are the same as the Allow header. set cache to one week for all Access-Control headers for CORS preflight only. remove self.client.setHeader("Access-Control-Allow-Origin", "*") and set Access-Control-Allow-Origin to the client supplied origin if it passes allowed origin checks. Required for CORS otherwise data isn't available to caller. Set for all responses. set Vary header now includes Origin as responses can differ based on Origin for all responses. set Access-Control-Allow-Credentials to true on all responses. test_liveserver.py: run server with setting to enforce origin csrf header check run server with setting to enforce x-requested-with csrf header check run server with setting for allowed_api_origins requests now set required csrf headers test preflight request on collections check new headers and Origin is no longer '*' rewrite all compression checks to use a single method with argument to use different compression methods. Reduce a lot of code duplication and makes updating for new headers easier. test_cgi: test new error messages in client.py account for new headers test preflight and new code paths

"""
In Python 3, sometimes TAL "python:" expressions that refer to
variables but not all variables are recognized. That is in Python 2.7
all variables used in a TAL "python:" expression are recognized as
references. In Python 3.5 (perhaps earlier), some TAL "python:"
expressions refer to variables but the reference generates an error
like this:

<class 'NameError'>: name 'some_tal_variable' is not defined

even when the variable is defined. Output after this message lists the
variable and its value.
"""

import unittest

from roundup.cgi.PageTemplates.PythonExpr import PythonExpr as PythonExprClass

class ExprTest(unittest.TestCase):
    def testExpr(self):
        expr = '[x for x in context.assignedto ' \
               'if x.realname not in user_realnames]'
        pe = PythonExprClass('test', expr, None)
        # Looking at the expression, only context and user_realnames are
        # external variables. The names assignedto and realname are members,
        # and x is local.
        required_names = ['context', 'user_realnames']
        got_names = pe._f_varnames
        for required_name in required_names:
            self.assertIn(required_name, got_names)