Fix pkg_resources warning

src/ops/__init__.py

@@ -8,19 +8,24 @@
 # OF ANY KIND, either express or implied. See the License for the specific language
 # governing permissions and limitations under the License.
 
-import pkg_resources
 import re
 from distutils.version import StrictVersion
 from subprocess import call, Popen, PIPE
 
 from six import PY3
 
 from .cli import display
+try:
+    from importlib import metadata as importlib_metadata
+except ImportError:
+    import importlib_metadata
 
 
 def validate_ops_version(min_ops_version):
-    current_ops_version = [
-        x.version for x in pkg_resources.working_set if x.project_name == "ops-cli"][0]
+    try:
+        current_ops_version = importlib_metadata.version("ops-cli")
+    except Exception:
+        raise Exception("Cannot determine current ops-cli version from installed metadata.")
     if StrictVersion(current_ops_version) < StrictVersion(min_ops_version):
         raise Exception("The current ops version {0} is lower than the minimum required version {1}. "
                         "Please upgrade by following the instructions seen here: "

src/ops/cli/terraform.py

@@ -17,7 +17,6 @@
 from ops.hierarchical.composition_config_generator import TerraformConfigGenerator
 from distutils.version import StrictVersion
 from ops import validate_ops_version
-import pkg_resources
 
 logger = logging.getLogger(__name__)