diff --git a/.travis.yml b/.travis.yml
index 7a2149e6..edd7a601 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,25 +8,54 @@ matrix:
       compiler: gcc
       env:
         - MAKETARGET="test-all tidy-all check-format"
+      addons:
+        apt:
+          sources:
+            - deadsnakes
+          packages:
+            - valgrind
+            - python3.7
     - os: linux
       compiler: clang
       env:
         - MAKETARGET=test-all
+      addons:
+        apt:
+          sources:
+            - deadsnakes
+          packages:
+            - valgrind
+            - python3.7
     - os: osx
+      osx_image: xcode10.1
       compiler: clang
       env:
         - MAKETARGET=test-all
-  # This currently appears to be broken.
-  # - os: osx
-  #   env:
-  #     - MATRIX_EVAL="brew install gcc && CC=gcc-8 && CXX=g++-8"
-  #     - MAKETARGET=test-all
+      addons:
+        homebrew:
+          packages:
+            - python@3.7
+    - os: osx
+      osx_image: xcode10.1
+      compiler: gcc
+      addons:
+        homebrew:
+          packages:
+            - gcc@8
+            - python@3.7
+      env:
+        - MAKETARGET=test-all
 
 before_install:
-  - eval "${MATRIX_EVAL}"
+  - python3.7 --version
+  - curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
+  - python3.7 get-pip.py --user
+  - python3.7 -mpip install -r requirements.txt
 
 script:
   - make ${MAKETARGET}
 
 
+cache: pip
+
 #  vim: set ft=yaml ts=2 sw=2 tw=0 et :
diff --git a/Makefile b/Makefile
index a51e476f..bd7d8eb4 100644
--- a/Makefile
+++ b/Makefile
@@ -149,22 +149,22 @@ run-valgrind-all:
 
 .PHONY: run-testvectors
 run-testvectors: test/check_testvectors.py | require_scheme
-	python3 test/check_testvectors.py $(SCHEME) || exit 1; \
+	python3.7 test/check_testvectors.py $(SCHEME) || exit 1; \
 
 .PHONY: run-symbol-namespace
 run-symbol-namespace: test/check_symbol_namespace.py | require_scheme
-	python3 test/check_symbol_namespace.py $(SCHEME) || exit 1; \
+	python3.7 test/check_symbol_namespace.py $(SCHEME) || exit 1; \
 
 .PHONY: run-testvectors-all
 run-testvectors-all: test/check_testvectors.py
 	@for scheme in $(ALL_SCHEMES); do \
-	    python3 test/check_testvectors.py $$scheme || exit 1; \
+	    python3.7 test/check_testvectors.py $$scheme || exit 1; \
 	done
 
 .PHONY: run-symbol-namespace-all
 run-symbol-namespace-all:
 	@for scheme in $(ALL_SCHEMES); do \
-	    python3 test/check_symbol_namespace.py $$scheme || exit 1; \
+	    python3.7 test/check_symbol_namespace.py $$scheme || exit 1; \
 	done
 
 .PHONY: run-functest-all
diff --git a/test/check_symbol_namespace.py b/test/check_symbol_namespace.py
index a28eb874..a6d1d4d6 100644
--- a/test/check_symbol_namespace.py
+++ b/test/check_symbol_namespace.py
@@ -16,8 +16,8 @@ SCHEMESHORT = SCHEME.split('/')[1].upper()
 namespace = f"PQCLEAN_{SCHEMESHORT}_".replace('-', '')
 
 # TODO can we do this using object files instead, to preserve file origin?
-sharedlib = f"bin/shared_{SCHEMEFULL}_clean.so"
-subprocess.run(["make", sharedlib, f"SCHEME={SCHEME}"])
+sharedlib = "bin/shared_{}_clean.so".format(SCHEMEFULL)
+subprocess.run(["make", sharedlib, "SCHEME={}".format(SCHEME)])
 p = subprocess.run(["nm", "-D", sharedlib], capture_output=True)
 
 symbols = p.stdout.decode('utf-8').strip().split("\n")
@@ -31,7 +31,7 @@ for symbolstr in symbols:
 
 if non_namespaced:
     print("! Not all symbols were properly namespaced.", file=sys.stderr)
-    print(f"! Missing namespace literal {namespace}", file=sys.stderr)
+    print("! Missing namespace literal {}".format(namespace), file=sys.stderr)
     for symbol in non_namespaced:
-        print(f"\t{symbol}", file=sys.stderr)
+        print("\t{}".format(symbol), file=sys.stderr)
     sys.exit(1)
diff --git a/test/check_testvectors.py b/test/check_testvectors.py
index 976052c5..65c1e2b5 100644
--- a/test/check_testvectors.py
+++ b/test/check_testvectors.py
@@ -17,24 +17,26 @@ SCHEME = sys.argv[1]
 SCHEMEFULL = SCHEME.replace('/', '_')  # e.g. crypto_kem_kyber768
 SCHEMESHORT = SCHEME.split('/')[1].upper()
 
+
 def get_hash(scheme):
-    with open(f"{scheme}/META.yml", 'r') as stream:
+    with open("{}/META.yml".format(scheme), 'r') as stream:
         meta = yaml.load(stream)
         return hex(meta['testvectors-sha3-256']).replace('0x', '')
 
 
 expectedTestvectorsHash = get_hash(SCHEME)
 
-subprocess.run(["make", "testvectors", f"SCHEME={SCHEME}"])
-implementations = [x for x in os.listdir('bin') if 'testvectors' in x and SCHEMEFULL in x]
+subprocess.run(["make", "testvectors", "SCHEME={}".format(SCHEME)])
+implementations = [
+    x for x in os.listdir('bin') if 'testvectors' in x and SCHEMEFULL in x]
 
 for impl in implementations:
-    testvectors = subprocess.run([f"bin/{impl}"],stdout=subprocess.PIPE)
+    testvectors = subprocess.run(["bin/{}".format(impl)],
+                                 stdout=subprocess.PIPE)
     testvectorsHash = hashlib.sha3_256(testvectors.stdout).hexdigest()
     if testvectorsHash.lower() != expectedTestvectorsHash.lower():
-        print(f"testvectors of {SCHEME} should be {expectedTestvectorsHash}, but is {testvectorsHash}")
+        print("testvectors of {} should be {}, but is {}"
+              .format(SCHEME, expectedTestvectorsHash, testvectorsHash))
         sys.exit(1)
     else:
-        print(f"testvectors of {SCHEME} matched expected hash")
-
-
+        print("testvectors of {} matched expected hash".format(SCHEME))