Fix drone CI script

closes #2243

.drone/linux-cxx-install.sh

@@ -35,6 +35,6 @@ fi
 
 if [ "$MAJOR_VERSION" -gt "18" ]; then
     sudo -E apt-get -o Acquire::Retries=3 -y install python3 python3-pip
-    ln -s /usr/bin/python3 /usr/bin/python
-    ln -s /usr/bin/pip3 /usr/bin/pip
+    ln -s /usr/bin/python3 /usr/bin/python || true
+    ln -s /usr/bin/pip3 /usr/bin/pip || true
 fi

CHANGELOG.md

@@ -1,3 +1,4 @@
+* Fix Drone CI script.
 * Add example of reading large response body.
 
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