Fix callRemote unicode issues on Python 2 universally, using monkeypatching.

src/allmydata/__init__.py

@@ -42,3 +42,9 @@ __full_version__ = __appname__ + '/' + str(__version__)
 # Install Python 3 module locations in Python 2:
 from future import standard_library
 standard_library.install_aliases()
+
+
+# Monkey-patch 3rd party libraries:
+from ._monkeypatch import patch
+patch()
+del patch

src/allmydata/_monkeypatch.py

@@ -0,0 +1,41 @@
+"""
+Monkey-patching of third party libraries.
+
+Ported to Python 3.
+"""
+
+
+from __future__ import unicode_literals
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from future.utils import PY2
+if PY2:
+    from future.builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, list, object, range, str, max, min  # noqa: F401
+
+
+def patch():
+    """Path third-party libraries to make Tahoe-LAFS work."""
+    # Make sure Foolscap always get native strings passed to method names in callRemote.
+    # This can be removed when any one of the following happens:
+    #
+    # 1. Tahoe-LAFS on Python 2 switches to version of Foolscap that fixes
+    #    https://github.com/warner/foolscap/issues/72
+    # 2. Foolscap is dropped as a dependency.
+    # 3. Tahoe-LAFS drops Python 2 support.
+
+    if PY2:
+        # Only tested with this version; ensure correctness with new releases,
+        # and then either update the assert or hopefully drop the monkeypatch.
+        from foolscap import __version__
+        assert __version__ == "0.13.1", "Wrong version %s of Foolscap" % (__version__,)
+
+        from foolscap.referenceable import RemoteReference
+        original_getMethodInfo = RemoteReference._getMethodInfo
+
+        def _getMethodInfo(self, name):
+            if isinstance(name, str):
+                name = name.encode("utf-8")
+            return original_getMethodInfo(self, name)
+        RemoteReference._getMethodInfo = _getMethodInfo

src/allmydata/immutable/downloader/share.py

@@ -6,7 +6,7 @@ from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
 
-from future.utils import PY2, native_str
+from future.utils import PY2
 if PY2:
     from future.builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, list, object, range, str, max, min  # noqa: F401
 
@@ -765,9 +765,7 @@ class Share(object):
                                  level=log.WEIRD, umid="qZu0wg"))
 
     def _send_request(self, start, length):
-        # For some reason tests fail on Python 2 if this is not a native
-        # string...
-        return self._rref.callRemote(native_str("read"), start, length)
+        return self._rref.callRemote("read", start, length)
 
     def _got_data(self, data, start, length, block_ev, lp):
         block_ev.finished(len(data), now())

src/allmydata/util/_python3.py

@@ -24,6 +24,7 @@ if PY2:
 
 # Keep these sorted alphabetically, to reduce merge conflicts:
 PORTED_MODULES = [
+    "allmydata._monkeypatch",
     "allmydata.codec",
     "allmydata.crypto",
     "allmydata.crypto.aes",