lxml 4.0.0 is required on PyPy

setup.py

@@ -21,7 +21,16 @@ def has_environment_marker_platform_impl_support():
 extras_require = {}
 
 if has_environment_marker_platform_impl_support():
+    extras_require[':platform_python_implementation == "CPython"'] = [
+        'lxml>=3.5.0',
+    ]
     extras_require[':platform_python_implementation == "PyPy"'] = [
+        # Earlier lxml versions are affected by
+        # https://bitbucket.org/pypy/pypy/issues/2498/cython-on-pypy-3-dict-object-has-no,
+        # which was fixed in Cython 0.26, released on 2017-06-19, and used to
+        # generate the C headers of lxml release tarballs published since then, the
+        # first of which was:
+        'lxml>=4.0.0',
         'PyPyDispatcher>=2.1.0',
     ]
 
@@ -71,7 +80,6 @@ setup(
         'Twisted>=17.9.0',
         'cryptography>=2.0',
         'cssselect>=0.9.1',
-        'lxml>=3.5.0',
         'parsel>=1.5.0',
         'PyDispatcher>=2.0.5',
         'pyOpenSSL>=16.2.0',

tox.ini

@@ -107,9 +107,8 @@ basepython = {[testenv:pypy3]basepython}
 commands = {[testenv:pypy3]commands}
 deps =
     {[pinned-common]deps}
-    # https://github.com/lxml/lxml/pull/187
-    lxml==3.6.0
-
+    lxml==4.0.0
+    PyPyDispatcher==2.1.0
 
 [docs]
 changedir = docs