pytest: Simple wrapper around BitcoinProxy to avoid timeouts

Running long integration tests could result in `bitcoind` dropping the
connection inbetween calls, and since python-bitcoinlib does not
reconnect and/or retry, all subsequent tests would fail as well. This
patch switches to throwaway connections, each serving just one
request. It's easier than to reach into the bitcoinlib to reconnect
and reauth, but comes with some overhead, but I think it's acceptable
for the few bitcoin calls we actually perform.

tests/utils.py

@@ -108,6 +108,31 @@ class TailableProc(object):
                 pos += 1
 
 
+class SimpleBitcoinProxy:
+    """Wrapper for BitcoinProxy to reconnect.
+
+    Long wait times between calls to the Bitcoin RPC could result in
+    `bitcoind` closing the connection, so here we just create
+    throwaway connections. This is easier than to reach into the RPC
+    library to close, reopen and reauth upon failure.
+    """
+    def __init__(self, url):
+        self.url = url
+
+    def __getattr__(self, name):
+        if name.startswith('__') and name.endswith('__'):
+            # Python internal stuff
+            raise AttributeError
+
+        # Create a callable to do the actual call
+        f = lambda *args: BitcoinProxy(self.url)._call(name, *args)
+
+        # Make debuggers show <function bitcoin.rpc.name> rather than <function
+        # bitcoin.rpc.<lambda>>
+        f.__name__ = name
+        return f
+
+
 class BitcoinD(TailableProc):
 
     def __init__(self, bitcoin_dir="/tmp/bitcoind-test", rpcport=18332):
@@ -134,7 +159,7 @@ class BitcoinD(TailableProc):
         BITCOIND_CONFIG['rpcport'] = rpcport
         write_config(os.path.join(bitcoin_dir, 'bitcoin.conf'), BITCOIND_CONFIG)
         write_config(os.path.join(regtestdir, 'bitcoin.conf'), BITCOIND_CONFIG)
-        self.rpc = BitcoinProxy(
+        self.rpc = SimpleBitcoinProxy(
             "http://rpcuser:rpcpass@127.0.0.1:{}".format(self.rpcport))
 
     def start(self):