I use %3D (URL encoded equal sign) prefix in argument name for filter parametrization:
GET /users?%3Dphone_number=1234567

Since request_param supports matching specific values with equal sign syntax, this doesn't work when route registered with explicit filter args names in request_param.

CHANGES.txt

@@ -10,6 +10,11 @@ unreleased
  ``[app:main]`` and ``[server:main]``.
  See https://github.com/Pylons/pyramid/pull/2292

- Allow a leading ``=`` on the key of the request param predicate.
  For example, '=abc=1' is equivalent down to
  ``request.params['=abc'] == '1'``.
  See https://github.com/Pylons/pyramid/pull/1370

1.6 (2015-04-14)
================

CONTRIBUTORS.txt

@@ -247,6 +247,8 @@ Contributors

- Donald Stufft, 2015/03/15

- Timur Izhbulatov, 2015/04/14

- Karen Dalton, 2015/06/01

- Igor Stroh, 2015/06/10

pyramid/config/predicates.py

@@ -70,7 +70,12 @@ def __init__(self, val, config):
        for p in val:
            k = p
            v = None
            if '=' in p:
            if p.startswith('='):
                if '=' in p[1:]:
                    k, v = p[1:].split('=', 1)
                    k = '=' + k
                    k, v = k.strip(), v.strip()
            elif '=' in p:
                k, v = p.split('=', 1)
                k, v = k.strip(), v.strip()
            reqs.append((k, v))

pyramid/tests/test_config/test_predicates.py

@@ -120,9 +120,9 @@ def test___call___true_withval(self):
        self.assertTrue(result)

    def test___call___true_multi(self):
        inst = self._makeOne(('abc', 'def =2 '))
        inst = self._makeOne(('abc', '=def =2= '))
        request = Dummy()
        request.params = {'abc':'1', 'def': '2'}
        request.params = {'abc':'1', '=def': '2='}
        result = inst(None, request)
        self.assertTrue(result)

@@ -144,6 +144,10 @@ def test_text_exists(self):
        inst = self._makeOne('abc')
        self.assertEqual(inst.text(), 'request_param abc')

    def test_text_exists_equal_sign(self):
        inst = self._makeOne('=abc')
        self.assertEqual(inst.text(), 'request_param =abc')

    def test_text_withval(self):
        inst = self._makeOne('abc=  1')
        self.assertEqual(inst.text(), 'request_param abc=1')
@@ -152,10 +156,18 @@ def test_text_multi(self):
        inst = self._makeOne(('abc=  1', 'def'))
        self.assertEqual(inst.text(), 'request_param abc=1,def')

    def test_text_multi_equal_sign(self):
        inst = self._makeOne(('abc=  1', '=def= 2'))
        self.assertEqual(inst.text(), 'request_param =def=2,abc=1')

    def test_phash_exists(self):
        inst = self._makeOne('abc')
        self.assertEqual(inst.phash(), 'request_param abc')

    def test_phash_exists_equal_sign(self):
        inst = self._makeOne('=abc')
        self.assertEqual(inst.phash(), 'request_param =abc')

    def test_phash_withval(self):
        inst = self._makeOne('abc=   1')
        self.assertEqual(inst.phash(), "request_param abc=1")