py38: switch to Python 3.8 (#29064)

This removes Python 3.6 from CI and devenv. Will be following up with some PRs for further cleanup.

Need to coordinate settings changes again.

.github/workflows/acceptance.yml

@@ -150,7 +150,7 @@ jobs:
     timeout-minutes: 20
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
         # XXX: When updating this, make sure you also update MATRIX_INSTANCE_TOTAL.
         instance: [0, 1, 2, 3]
     env:
@@ -215,7 +215,7 @@ jobs:
     timeout-minutes: 30
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
         # XXX: When updating this, make sure you also update MATRIX_INSTANCE_TOTAL.
         instance: [0]
     env:

.github/workflows/api-docs-test.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
     steps:
       - uses: actions/checkout@v2
 

.github/workflows/backend-lint.yml

@@ -12,7 +12,7 @@ jobs:
     timeout-minutes: 10
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
     steps:
       - uses: actions/checkout@v2
 

.github/workflows/backend-test.yml

@@ -13,7 +13,7 @@ jobs:
     timeout-minutes: 20
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
         # XXX: When updating this, make sure you also update MATRIX_INSTANCE_TOTAL.
         instance: [0, 1, 2]
 

.github/workflows/backend-typing.yml

@@ -12,8 +12,7 @@ jobs:
     timeout-minutes: 12
     strategy:
       matrix:
-        # TODO(joshuarli): Switch to 3.8.12 when we switch over to Python 3.8.
-        python-version: [3.6.13]
+        python-version: [3.8.12]
     steps:
       - uses: actions/checkout@v2
 

.github/workflows/check-if-migration-is-required.yml

@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
     needs: [should-check]
 
     steps:

.github/workflows/command-line-test.yml

@@ -12,7 +12,7 @@ jobs:
     timeout-minutes: 10
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
     steps:
       - uses: actions/checkout@v2
 

.github/workflows/development-environment.yml

@@ -22,7 +22,7 @@ jobs:
         # Using Ubuntu 18 until I figure out this error:
         # -> ImportError: libffi.so.6: cannot open shared object file: No such file or directory
         os: [macos-11.0, ubuntu-18.04]
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
       fail-fast: false
     env:
       PIP_DISABLE_PIP_VERSION_CHECK: on

.github/workflows/migrations.yml

@@ -41,7 +41,7 @@ jobs:
     timeout-minutes: 8
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
     needs: did-migration-change
     if: ${{ needs.did-migration-change.outputs.added == 'true' }}
 

.github/workflows/plugins-test.yml

@@ -13,7 +13,7 @@ jobs:
     timeout-minutes: 10
     strategy:
       matrix:
-        python-version: [3.6.13, 3.8.12]
+        python-version: [3.8.12]
     steps:
       - uses: actions/checkout@v2