deprecate PystoreConnector and ArcticConnectors

- remove optional install options for these connectors from pyproject.toml

pastastore/connectors.py

@@ -29,6 +29,12 @@ def __init__(self, name: str, connstr: str):
         connstr : str
             connection string (e.g. 'mongodb://localhost:27017/')
         """
+        warnings.warn(
+            "ArcticConnector is deprecated. Please use a different "
+            "connector, e.g. `pst.ArcticDBConnector`.",
+            DeprecationWarning,
+            stacklevel=1,
+        )
         try:
             import arctic
         except ModuleNotFoundError as e:
@@ -392,6 +398,12 @@ def __init__(self, name: str, path: str):
         path : str
             path to the pystore directory
         """
+        warnings.warn(
+            "PystoreConnector is deprecated. Please use a different "
+            "connector, e.g. `pst.PasConnector`.",
+            DeprecationWarning,
+            stacklevel=1,
+        )
         try:
             import pystore
         except ModuleNotFoundError as e:

pyproject.toml

@@ -58,16 +58,9 @@ test = [
     "pytest-dependency",
     "pytest-benchmark",
     "codacy-coverage",
-    "lxml",                               # temporary fix: for hydropandas 0.8.0
+    "lxml",
 ]
-pystore = ["fsspec>=0.3.3", "python-snappy", "dask[dataframe]"]
-arctic = [
-    "arctic", # will not work as releases not uploaded to PyPI
-]
-arcticdb = [
-    "arcticdb",
-    "protobuf~=4.0",
-] # TODO: temporarily set protobuf to version 4
+arcticdb = ["arcticdb"]
 docs = [
     "pastastore[optional]",
     "sphinx_rtd_theme",