update mypy to 0.790 (#4581)

Author: mathause

.pre-commit-config.yaml

@@ -19,7 +19,7 @@ repos:
     hooks:
       - id: flake8
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v0.782  # Must match ci/requirements/*.yml
+    rev: v0.790  # Must match ci/requirements/*.yml
     hooks:
       - id: mypy
   # run this occasionally, ref discussion https://github.com/pydata/xarray/pull/3194

ci/requirements/py36.yml

@@ -22,7 +22,7 @@ dependencies:
   - isort
   - lxml    # Optional dep of pydap
   - matplotlib
-  - mypy=0.782  # Must match .pre-commit-config.yaml
+  - mypy=0.790  # Must match .pre-commit-config.yaml
   - nc-time-axis
   - netcdf4
   - numba

ci/requirements/py37-windows.yml

@@ -22,7 +22,7 @@ dependencies:
   - isort
   - lxml    # Optional dep of pydap
   - matplotlib
-  - mypy=0.782  # Must match .pre-commit-config.yaml
+  - mypy=0.790  # Must match .pre-commit-config.yaml
   - nc-time-axis
   - netcdf4
   - numba

ci/requirements/py37.yml

@@ -22,7 +22,7 @@ dependencies:
   - isort
   - lxml    # Optional dep of pydap
   - matplotlib
-  - mypy=0.782  # Must match .pre-commit-config.yaml
+  - mypy=0.790  # Must match .pre-commit-config.yaml
   - nc-time-axis
   - netcdf4
   - numba

ci/requirements/py38-all-but-dask.yml

@@ -19,7 +19,7 @@ dependencies:
   - isort
   - lxml    # Optional dep of pydap
   - matplotlib
-  - mypy=0.782  # Must match .pre-commit-config.yaml
+  - mypy=0.790  # Must match .pre-commit-config.yaml
   - nc-time-axis
   - netcdf4
   - numba

ci/requirements/py38.yml

@@ -22,7 +22,7 @@ dependencies:
   - isort
   - lxml    # Optional dep of pydap
   - matplotlib
-  - mypy=0.782  # Must match .pre-commit-config.yaml
+  - mypy=0.790  # Must match .pre-commit-config.yaml
   - nc-time-axis
   - netcdf4
   - numba

xarray/core/utils.py

@@ -463,7 +463,8 @@ def __delitem__(self, key: K) -> None:
         del self.mapping[key]
 
     def __iter__(self) -> Iterator[K]:
-        return iter(sorted(self.mapping))
+        # see #4571 for the reason of the type ignore
+        return iter(sorted(self.mapping))  # type: ignore
 
     def __len__(self) -> int:
         return len(self.mapping)