Pin pytest to 5.3.5, and bitcoind download for travis

As of 13 March the latest pytest breaks the twisted tests.
As a result the version is pinned until that can be fixed.
Additionally, at the same time, the bitcoin ppa has been
removed and so cannot be used in our travis testing setup.
Hence we install bitcoin directly (for tests only, of course)
from bitcoin.org,
copying bitcoind and bitcoin-cli to `/usr/local/lib`.

.travis.yml

@@ -14,11 +14,7 @@ matrix:
       env: PIP_DOWNLOAD_CACHE=$HOME/.cache/pip
       addons:
         apt:
-           sources:
-           - sourceline: 'ppa:bitcoin/bitcoin'
-             key_url: 'http://keyserver.ubuntu.com:11371/pks/lookup?op=get&search=0xD46F45428842CE5E'
            packages:
-             - bitcoind
              - python3-dev
              - python3-pip
              - python-virtualenv
@@ -46,6 +42,7 @@ before_install:
   - do_on osx pip install virtualenv
 cache:
   directories:
+   - $HOME/bitcoin/bitcoin-0.19.1/bin
    - $HOME/downloads
    - $HOME/.cache/pip
    - $HOME/Library/Caches/pip
@@ -56,6 +53,7 @@ install:
   - mkdir -p "$HOME/downloads"
   - mkdir -p "$TRAVIS_BUILD_DIR/deps/cache/"
   - find "$HOME/downloads" -type f -exec cp -v {} "$TRAVIS_BUILD_DIR/deps/cache/" \;
+  - on_host do_on linux ./install_bitcoind.sh
   - on_host do_on linux ./install.sh --develop --with-qt
   - on_host do_on osx virtualenv --python=python3 jmvenv
   - on_host find "$TRAVIS_BUILD_DIR/deps/cache/" -type f -exec cp -v {} "$HOME/downloads/" \;

install_bitcoind.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+set -ev
+
+export BITCOIND_VERSION=0.19.1
+
+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
+else
+        mkdir -p ~/bitcoin && \
+        pushd ~/bitcoin && \
+        wget https://bitcoin.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 && \
+        popd
+fi
+
+

requirements/testing.txt

@@ -3,7 +3,7 @@
 # numpy
 pexpect
 coverage==4.0.3
-pytest
+pytest==5.3.5
 pytest-cov>=2.4.0,<2.6
 python-coveralls
 mock