Merge ElementsProject/elements#1036: Rewrite assets tutorial

1d2dacb1e2 assets_tutorial: basically rewrite the whole thing (Andrew Poelstra)
6a74528a40 assets_tutorial: clean up PIDs and temp directories correctly (Andrew Poelstra)
6bd3df60e0 assets_tutorial: fix argument and path handling (Andrew Poelstra)

Pull request description:

  Clean up and rewrite the assets tutorial

  * Updates RPC to handle 0.21 changes (you now need createwallet/loadwallet)
  * Cleans up stray processes and temp directories even when it crashes
  * Significantly expands comments
  * Modernizes the Python, removes weird idioms like calling `raise` in an `except: pass` block

ACKs for top commit:
  gwillen:
    utACK 1d2dacb.

Tree-SHA512: dae8c7e02d3f5aa56cc714034667d3efdbc307744ec86d348cfccf117db80989e4089e095563ba8d91c4bab762972c3fd75ec0da2bd66c5ec0bb8449eae0fdcd

contrib/assets_tutorial/bitcoin.conf

@@ -1,9 +1,20 @@
 regtest=1
-daemon=1
 txindex=1
-
-regtest.rpcport=18888
-regtest.port=18889
+# We are spawning these inside a Python script which will manage them, so don't daemonize
+daemon=0
+# Extra debugging output in case things go wrong
+debug=1
+debugexclude=libevent
+debugexclude=leveldb
+printtoconsole=0
 
 rpcuser=user3
 rpcpassword=password3
+
+# Set a fallback fee, since initially the nodes will have no transaction data
+# to do fee estimation from
+fallbackfee=0.0002
+
+[regtest]
+rpcport=18888
+port=18889

contrib/assets_tutorial/elements1.conf

@@ -3,19 +3,20 @@ chain=elementsregtest
 # Standard bitcoind stuff
 rpcuser=user1
 rpcpassword=password1
-elementsregtest.rpcport=18884
-elementsregtest.port=18886
 
-rpcport=18884
-# Over p2p we will only connect to local other elementsd
-elementsregtest.connect=localhost:18887
 
-daemon=1
+# We are spawning these inside a Python script which will manage them, so don't daemonize
+daemon=0
 # Make sure you set listen after -connect, otherwise neither
 # will accept incoming connections!
 listen=1
 # Just for looking at random txs
 txindex=1
+# Extra debugging output in case things go wrong
+debug=1
+debugexclude=libevent
+debugexclude=leveldb
+printtoconsole=0
 
 # This is the script that controls pegged in funds in Bitcoin network
 # Users will be pegging into a P2SH of this, and the "watchmen"
@@ -42,3 +43,12 @@ mainchainrpcpassword=password3
 
 # Free money to make testing easier
 initialfreecoins=2100000000000000
+
+# Set a fallback fee, since initially the nodes will have no transaction data
+# to do fee estimation from
+fallbackfee=0.0002
+
+[elementsregtest]
+rpcport=18884
+port=18886
+

contrib/assets_tutorial/elements2.conf

@@ -2,13 +2,16 @@ chain=elementsregtest
 
 rpcuser=user2
 rpcpassword=password2
-elementsregtest.rpcport=18885
-elementsregtest.port=18887
-elementsregtest.connect=localhost:18886
 
-daemon=1
+# We are spawning these inside a Python script which will manage them, so don't daemonize
+daemon=0
 listen=1
 txindex=1
+# Extra debugging output in case things go wrong
+debug=1
+debugexclude=libevent
+debugexclude=leveldb
+printtoconsole=0
 
 #fedpegscript=51<pubkey>51ae
 #signblockscript=51<pubkey2>51ae
@@ -19,3 +22,12 @@ mainchainrpcpassword=password3
 validatepegin=1
 
 initialfreecoins=2100000000000000
+
+# Set a fallback fee, since initially the nodes will have no transaction data
+# to do fee estimation from
+fallbackfee=0.0002
+
+[elementsregtest]
+rpcport=18885
+port=18887
+