travis-ci: freeze curl version on 7.65.0 on OS X

Homebrew now contains curl-7.65.1 which affected by curl/curl#3995 (this
problem leads to segfaults). The next version is not released yet. The
current commit downgrades the curl version to 7.65.0.

Close #4288

.travis.mk

@@ -91,6 +91,12 @@ deps_osx:
 	brew update
 	brew install openssl readline curl icu4c --force
 	python2 -V || brew install python2 --force
+	###################################################
+	# Temporary workaround to curl version from
+	# issue #4288 to downgrade from 7.65.1 to 7.65.0:
+	# TODO: remove the workaround after 7.65.2 released
+	brew reinstall https://raw.githubusercontent.com/Homebrew/homebrew-core/e47f3e2682fa3d8a6ee58ded40718a1326e08a6d/Formula/curl.rb
+	###################################################
 	curl --silent --show-error --retry 5 https://bootstrap.pypa.io/get-pip.py >get-pip.py
 	python get-pip.py --user
 	pip install --user --force-reinstall -r test-run/requirements.txt