Fixed reading RELEASE in make.

Makefile

@@ -11,8 +11,8 @@ COVERAGE_PATH := docs/build/html/coverage
 
 # $(file) may not work depending upon version of make.
 #RELEASE := $(strip $(file < RELEASE.txt))
-RELEASE := $(strip `cat RELEASE.txt`)
+RELEASE := $(strip $(shell cat RELEASE.txt))
-VERSION := $(strip `cat VERSION.txt`)
+VERSION := $(strip $(shell cat VERSION.txt))
 DOCS_PATH := $(PROJECT_HOME)/docs_diff6_com
 DOCS_WWW := $(DOCS_PATH)/www
 
@@ -74,7 +74,6 @@ publish:
 secure:
 	bandit -r $(PACKAGE_NAME);
 
-
 #> support - Build support (help) and reference documentation.
 support:
 	cd docs && make dirhtml;