Switch to python 3

Makefile

@@ -1,4 +1,4 @@
-python := "$(shell { command -v python2.7 || command -v python; } 2>/dev/null)"
+python := "$(shell { command -v python3.6 || command -v python; } 2>/dev/null)"
 install_where := $(shell $(python) -c "import sys; print('' if hasattr(sys, 'real_prefix') else '--user')")
 
 # Set the relative path to installed binaries under the project virtualenv.
@@ -27,7 +27,7 @@ env: requirements*.txt
 
 rehash-requirements:
 	for f in requirements*.txt; do \
-	    sed -r -e '/^ +--hash/d' -e 's/\\$$//' $$f | xargs ./env/bin/hashin -r $$f -p 2.7 -p 3.6; \
+	    sed -r -e '/^ +--hash/d' -e 's/\\$$//' $$f | xargs ./env/bin/hashin -r $$f -p 3.4 -p 3.6; \
 	done
 
 clean:

README.md

@@ -74,7 +74,7 @@ The python code inside simplates is only for request-specific logic, common back
 
 Firstly, make sure you have the following dependencies installed:
 
-- python ≥ 2.7.12 (the code is compatible with python 3, but production still runs on python 2 for now)
+- python ≥ 3.6
   - including the C headers of python and libffi, which are packaged separately in many Linux distributions
 - postgresql 9.6 (see [the official download & install docs](https://www.postgresql.org/download/))
 - make
@@ -178,7 +178,7 @@ All new dependencies need to be audited to check that they don't contain malicio
 We use [pip's Hash-Checking Mode](https://pip.pypa.io/en/stable/reference/pip_install/#hash-checking-mode) to protect ourselves from dependency tampering. Thus when adding or upgrading a dependency the new hashes need to computed and put in the requirements file. For that you can use [hashin](https://github.com/peterbe/hashin):
 
     pip install hashin
-    hashin package==x.y -r requirements_base.txt -p 2.7 -p 3.4 -p 3.6
+    hashin package==x.y -r requirements_base.txt -p 3.4 -p 3.6
     # note: we have several requirements files, use the right one
 
 If for some reason you need to rehash all requirements, run `make rehash-requirements`.

liberapay/main.py

@@ -235,7 +235,8 @@ def _Querystring_derive(self, **kw):
     raise Warning('pando.http.request.Request.source already exists')
 def _source(self):
     def f():
-        addr = ip_address(self.environ[b'REMOTE_ADDR'].decode('ascii'))
+        addr = self.environ.get('REMOTE_ADDR') or self.environ[b'REMOTE_ADDR']
+        addr = ip_address(addr.decode('ascii') if type(addr) is bytes else addr)
         trusted_proxies = getattr(self.website, 'trusted_proxies', None)
         forwarded_for = self.headers.get(b'X-Forwarded-For')
         self.__dict__['bypasses_proxy'] = bool(trusted_proxies)