Refactor exception classes #535

Job	Run time	Billable time
test-postgres (9.5)	4m 14s	0s
test-platforms (3.8, ubuntu-latest, asyncio)	3m 25s	0s
test-postgres (9.6)	5m 54s	0s
test-platforms (3.8, ubuntu-latest, uvloop)	3m 8s	0s
test-postgres (10)	3m 36s	0s
test-platforms (3.8, macos-latest, asyncio)	2m 52s	0s
test-postgres (11)	3m 54s	0s
test-platforms (3.8, macos-latest, uvloop)	2m 34s	0s
test-postgres (12)	3m 30s	0s
test-platforms (3.8, windows-latest, asyncio)	5m 51s	0s
test-postgres (13)	4m 5s	0s
test-platforms (3.9, ubuntu-latest, asyncio)	3m 12s	0s
test-postgres (14)	3m 36s	0s
test-platforms (3.9, ubuntu-latest, uvloop)	3m 16s	0s
test-postgres (15)	3m 48s	0s
test-platforms (3.9, macos-latest, asyncio)	2m 48s	0s
test-postgres (16)	3m 44s	0s
test-platforms (3.9, macos-latest, uvloop)	2m 21s	0s
test-platforms (3.9, windows-latest, asyncio)	5m 56s	0s
test-platforms (3.10, ubuntu-latest, asyncio)	3m 24s	0s
test-platforms (3.10, ubuntu-latest, uvloop)	3m 15s	0s
test-platforms (3.10, macos-latest, asyncio)	3m 8s	0s
test-platforms (3.10, macos-latest, uvloop)	3m 34s	0s
test-platforms (3.10, windows-latest, asyncio)	5m 45s	0s
test-platforms (3.11, ubuntu-latest, asyncio)	3m 20s	0s
test-platforms (3.11, ubuntu-latest, uvloop)	2m 56s	0s
test-platforms (3.11, macos-latest, asyncio)	4m 3s	0s
test-platforms (3.11, macos-latest, uvloop)	3m 3s	0s
test-platforms (3.11, windows-latest, asyncio)	5m 47s	0s
test-platforms (3.12, ubuntu-latest, asyncio)	3m 45s	0s
test-platforms (3.12, macos-latest, asyncio)	2m 57s	0s
test-platforms (3.12, windows-latest, asyncio)	6m 0s	0s
Regression Tests	0s	0s
	2h 2m 41s	0s

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