Use pytest instead of nosetests

Nose has been in maintenance mode for the past several years
and pytest is a good replacement.

Other changes:
- Replace deprecated assertRegexpMatches with assertRegex
- Replace deprecated assertRaisesRegexp with assertRaisesRegex
- Replace deprecated SafeConfigParser with ConfigParser
- Force reinstall pytest and mock in tox virtualenv. This is because
  the globally installed packages may not work as expected(occured in
  jenkins job).

JIRA: RHELCMP-1619
Signed-off-by: Haibo Lin <hlin@redhat.com>

Makefile

@@ -9,7 +9,7 @@ PKGRPMFLAGS=--define "_topdir ${PWD}" --define "_specdir ${PWD}" --define "_sour
 RPM="noarch/${PKGNAME}-$(VERSION)-$(RELEASE).noarch.rpm"
 SRPM="${PKGNAME}-$(VERSION)-$(RELEASE).src.rpm"
 
-NOSE=nosetests
+PYTEST=pytest
 
 
 all: help
@@ -95,10 +95,10 @@ clean:
 
 
 test:
-	$(NOSE) --exe $(NOSE_OPTS)
+	$(PYTEST) $(PYTEST_OPTS)
 
 test-coverage:
-	$(NOSE) --exe --with-cov --cov-report html --cov-config tox.ini $(NOSE_OPTS)
+	$(PYTEST) --cov=pungi --cov-report term --cov-report html --cov-config tox.ini $(PYTEST_OPTS)
 
 test-data:
 	./tests/data/specs/build.sh