GitHub workflow update (Python and Bitcoin Core versions)

* Remove Python 3.6 (EOL), add Python 3.10.
* Add support for testing against multiple Bitcoin Core versions, add
  0.18.0 (oldest officially support for test suite) and 22.0 (latest
  stable release). Previously we tested against hardcoded 0.19.1. IMO
  testing against oldest supported and latest makes sense, if tests pass
  on both, they should pass on releases inbetween too, unless there is
  some behaviour affecting us changed twice.

Also changed Core downloads from bitcoin.org to bitcoincore.org.

.github/workflows/unittests.yml

@@ -8,7 +8,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: ["3.7", "3.8", "3.9", "3.10"]
+        bitcoind-version: ["0.18.0", "22.0"]
 
     steps:
       - uses: actions/checkout@v2
@@ -38,10 +39,13 @@ jobs:
         uses: actions/cache@v2
         env:
           cache-name: bitcoind
+          BITCOIND_VERSION: ${{ matrix.bitcoind-version }}
         with:
           path: ~/bitcoin/*/bin/bitcoin*
           key: ${{ runner.os }}-${{ env.cache-name }}-${{ hashFiles('test/testrunner/install_bitcoind.sh') }}
       - name: Install bitcoind
+        env:
+          BITCOIND_VERSION: ${{ matrix.bitcoind-version }}
         run: ./test/testrunner/install_bitcoind.sh
       - name: Cache miniircd
         uses: actions/cache@v2

test/testrunner/install_bitcoind.sh

@@ -2,16 +2,19 @@
 
 set -ev
 
-export BITCOIND_VERSION=0.19.1
+if [[ -z "$BITCOIND_VERSION" ]]; then
+    echo "BITCOIND_VERSION must be set"
+    exit 1
+fi
 
 if sudo cp ~/bitcoin/bitcoin-$BITCOIND_VERSION/bin/bitcoind /usr/local/bin/bitcoind
 then
         echo "found cached bitcoind"
-	sudo cp ~/bitcoin/bitcoin-$BITCOIND_VERSION/bin/bitcoin-cli /usr/local/bin/bitcoin-cli
+        sudo cp ~/bitcoin/bitcoin-$BITCOIND_VERSION/bin/bitcoin-cli /usr/local/bin/bitcoin-cli
 else
         mkdir -p ~/bitcoin && \
         pushd ~/bitcoin && \
-        wget https://bitcoin.org/bin/bitcoin-core-$BITCOIND_VERSION/bitcoin-$BITCOIND_VERSION-x86_64-linux-gnu.tar.gz && \
+        wget https://bitcoincore.org/bin/bitcoin-core-$BITCOIND_VERSION/bitcoin-$BITCOIND_VERSION-x86_64-linux-gnu.tar.gz && \
         tar xvfz bitcoin-$BITCOIND_VERSION-x86_64-linux-gnu.tar.gz && \
         sudo cp ./bitcoin-$BITCOIND_VERSION/bin/bitcoind /usr/local/bin/bitcoind && \
         sudo cp ./bitcoin-$BITCOIND_VERSION/bin/bitcoin-cli /usr/local/bin/bitcoin-cli && \