Travis: don't install requirements.txt if we're just building.

This tests our instructions in INSTALL.md, which say you only need
requirements.txt for development or running tests, not building.

Also removes the unused SOURCE_CHECK_ONLY flag.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

.travis.yml

@@ -9,6 +9,7 @@ before_install:
 
 env:
   # These run superficial checks that don't take too long on their own
+  - ARCH=64 TEST_CMD="make" NO_PYTHON=1
   - ARCH=64 TEST_CMD="make check-source check-units installcheck" COPTFLAGS="-O3"
   - ARCH=32 TEST_CMD="make check-source check-units installcheck" DEVELOPER=0
   - ARCH=64 TEST_CMD="make check-source check-units installcheck" DEVELOPER=0 COMPILER=gcc-4.8

.travis/build.sh

@@ -6,12 +6,12 @@ export SLOW_MACHINE=1
 export CC=${COMPILER:-gcc}
 export DEVELOPER=${DEVELOPER:-1}
 export EXPERIMENTAL_FEATURES=${EXPERIMENTAL_FEATURES:-0}
-export SOURCE_CHECK_ONLY=${SOURCE_CHECK_ONLY:-"false"}
 export COMPAT=${COMPAT:-1}
 export PATH=$CWD/dependencies/bin:"$HOME"/.local/bin:"$PATH"
 export PYTEST_PAR=2
 export PYTEST_SENTRY_ALWAYS_REPORT=1
 export BOLTDIR=lightning-rfc
+
 # Allow up to 4 concurrent tests when not under valgrind, which might run out of memory.
 if [ "$VALGRIND" = 0 ]; then
     PYTEST_PAR=4
@@ -28,22 +28,28 @@ if [ ! -f dependencies/bin/bitcoind ]; then
     rm -rf bitcoin-0.20.1-x86_64-linux-gnu.tar.gz bitcoin-0.20.1
 fi
 
-pyenv global 3.7
+if [ "$NO_PYTHON" != 1 ]; then
+    pyenv global 3.7
+
+    pip3 install --user -U --quiet --progress-bar off \
+	 pip \
+	 pytest-test-groups==1.0.3
 
-# Update pip first, may save us the compilation of binary packages in the next call
-pip3 install --user -U --quiet --progress-bar off \
-     pip \
-     pytest-test-groups==1.0.3
+    pip3 install --user -U --quiet --progress-bar off \
+	 -r requirements.txt \
+	 -r contrib/pyln-client/requirements.txt \
+	 -r contrib/pyln-proto/requirements.txt \
+	 -r contrib/pyln-testing/requirements.txt
 
-pip3 install --user -U --quiet --progress-bar off \
-     -r requirements.txt \
-     -r contrib/pyln-client/requirements.txt \
-     -r contrib/pyln-proto/requirements.txt \
-     -r contrib/pyln-testing/requirements.txt
+    pip3 install --user -U --quiet --progress-bar off \
+	 pytest-sentry \
+	 pytest-rerunfailures
 
-pip3 install --user -U --quiet --progress-bar off \
-     pytest-sentry \
-     pytest-rerunfailures
+   cat > pytest.ini << EOF
+[pytest]
+addopts=-p no:logging --color=no --reruns=5
+EOF
+fi
 
 echo "Configuration which is going to be built:"
 echo -en 'travis_fold:start:script.1\\r'
@@ -51,11 +57,6 @@ echo -en 'travis_fold:start:script.1\\r'
 cat config.vars
 echo -en 'travis_fold:end:script.1\\r'
 
-cat > pytest.ini << EOF
-[pytest]
-addopts=-p no:logging --color=no --reruns=5
-EOF
-
 git clone https://github.com/lightningnetwork/lightning-rfc.git
 
 if [ "$TARGET_HOST" == "arm-linux-gnueabihf" ] || [ "$TARGET_HOST" == "aarch64-linux-gnu" ]