diff --git a/charmhelpers/__init__.py b/charmhelpers/__init__.py
index 61ef9071..1f57ed2a 100644
--- a/charmhelpers/__init__.py
+++ b/charmhelpers/__init__.py
@@ -49,7 +49,8 @@ __deprecated_functions = {}
 
 def deprecate(warning, date=None, log=None):
     """Add a deprecation warning the first time the function is used.
-    The date, which is a string in semi-ISO8660 format indicate the year-month
+
+    The date which is a string in semi-ISO8660 format indicates the year-month
     that the function is officially going to be removed.
 
     usage:
@@ -62,10 +63,11 @@ def deprecate(warning, date=None, log=None):
     The reason for passing the logging function (log) is so that hookenv.log
     can be used for a charm if needed.
 
-    :param warning:  String to indicat where it has moved ot.
-    :param date: optional sting, in YYYY-MM format to indicate when the
+    :param warning: String to indicate what is to be used instead.
+    :param date: Optional string in YYYY-MM format to indicate when the
                  function will definitely (probably) be removed.
-    :param log: The log function to call to log.  If not, logs to stdout
+    :param log: The log function to call in order to log. If None, logs to
+                stdout
     """
     def wrap(f):
 
diff --git a/charmhelpers/contrib/charmsupport/nrpe.py b/charmhelpers/contrib/charmsupport/nrpe.py
index eb6f8c08..14b80d96 100644
--- a/charmhelpers/contrib/charmsupport/nrpe.py
+++ b/charmhelpers/contrib/charmsupport/nrpe.py
@@ -411,7 +411,7 @@ def add_init_service_checks(nrpe, services, unit_name, immediate_check=True):
         upstart_init = '/etc/init/%s.conf' % svc
         sysv_init = '/etc/init.d/%s' % svc
 
-        if host.init_is_systemd():
+        if host.init_is_systemd(service_name=svc):
             nrpe.add_check(
                 shortname=svc,
                 description='process check {%s}' % unit_name,
diff --git a/charmhelpers/core/host.py b/charmhelpers/core/host.py
index b33ac906..a785efdf 100644
--- a/charmhelpers/core/host.py
+++ b/charmhelpers/core/host.py
@@ -193,7 +193,7 @@ def service_pause(service_name, init_dir="/etc/init", initd_dir="/etc/init.d",
         stopped = service_stop(service_name, **kwargs)
     upstart_file = os.path.join(init_dir, "{}.conf".format(service_name))
     sysv_file = os.path.join(initd_dir, service_name)
-    if init_is_systemd():
+    if init_is_systemd(service_name=service_name):
         service('disable', service_name)
         service('mask', service_name)
     elif os.path.exists(upstart_file):
@@ -227,7 +227,7 @@ def service_resume(service_name, init_dir="/etc/init",
     """
     upstart_file = os.path.join(init_dir, "{}.conf".format(service_name))
     sysv_file = os.path.join(initd_dir, service_name)
-    if init_is_systemd():
+    if init_is_systemd(service_name=service_name):
         service('unmask', service_name)
         service('enable', service_name)
     elif os.path.exists(upstart_file):
@@ -257,7 +257,7 @@ def service(action, service_name, **kwargs):
     :param **kwargs: additional params to be passed to the service command in
                     the form of key=value.
     """
-    if init_is_systemd():
+    if init_is_systemd(service_name=service_name):
         cmd = ['systemctl', action, service_name]
     else:
         cmd = ['service', service_name, action]
@@ -281,7 +281,7 @@ def service_running(service_name, **kwargs):
                      units (e.g. service ceph-osd status id=2). The kwargs
                      are ignored in systemd services.
     """
-    if init_is_systemd():
+    if init_is_systemd(service_name=service_name):
         return service('is-active', service_name)
     else:
         if os.path.exists(_UPSTART_CONF.format(service_name)):
@@ -311,8 +311,14 @@ def service_running(service_name, **kwargs):
 SYSTEMD_SYSTEM = '/run/systemd/system'
 
 
-def init_is_systemd():
-    """Return True if the host system uses systemd, False otherwise."""
+def init_is_systemd(service_name=None):
+    """
+    Returns whether the host uses systemd for the specified service.
+
+    @param Optional[str] service_name: specific name of service
+    """
+    if str(service_name).startswith("snap."):
+        return True
     if lsb_release()['DISTRIB_CODENAME'] == 'trusty':
         return False
     return os.path.isdir(SYSTEMD_SYSTEM)
diff --git a/requirements.txt b/requirements.txt
index 343beed1..2316401b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -13,5 +13,9 @@ netifaces>=0.10.4
 netaddr>=0.7.12,!=0.7.16
 Jinja2>=2.6  # BSD License (3 clause)
 six>=1.9.0
-dnspython>=1.12.0
+
+# dnspython 2.0.0 dropped py3.5 support
+dnspython<2.0.0; python_version < '3.6'
+dnspython; python_version >= '3.6'
+
 psutil>=1.1.1,<2.0.0
diff --git a/test-requirements.txt b/test-requirements.txt
index 44b50231..7d9c2587 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -10,7 +10,7 @@
 charm-tools>=2.4.4
 requests>=2.18.4
 mock>=1.2
-flake8>=2.2.4
+flake8>=2.2.4,<=2.4.1
 stestr>=2.2.0
 coverage>=4.5.2
 pyudev              # for ceph-* charm unit tests (need to fix the ceph-* charm unit tests/mocking)
diff --git a/tox.ini b/tox.ini
index 8080ba6d..b835733a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -116,5 +116,5 @@ commands =
     functest-run-suite --keep-model --bundle {posargs}
 
 [flake8]
-ignore = E402,E226,W504
+ignore = E402,E226
 exclude = */charmhelpers