Accept "17rc1" as server version in tests

The old coding assumed that PG server versions would always contain a
dot, but that's not true while in beta or rc.

test/dbapi/conftest.py

@@ -2,6 +2,8 @@
 
 import pytest
 
+from test.utils import parse_server_version
+
 import pg8000.dbapi
 
 
@@ -57,5 +59,5 @@ def pg_version(cursor):
     cursor.execute("select current_setting('server_version')")
     retval = cursor.fetchall()
     version = retval[0][0]
-    idx = version.index(".")
-    return int(version[:idx])
+    major = parse_server_version(version)
+    return int(major)

test/native/conftest.py

@@ -2,6 +2,8 @@
 
 import pytest
 
+from test.utils import parse_server_version
+
 import pg8000.native
 
 
@@ -45,5 +47,5 @@ def fin():
 def pg_version(con):
     retval = con.run("select current_setting('server_version')")
     version = retval[0][0]
-    idx = version.index(".")
-    return int(version[:idx])
+    major = parse_server_version(version)
+    return int(major)

test/test_utils.py

@@ -0,0 +1,5 @@
+from test.utils import parse_server_version
+
+
+def test_parse_server_version():
+    assert parse_server_version("17rc1") == 17

test/utils.py

@@ -0,0 +1,6 @@
+import re
+
+
+def parse_server_version(version):
+    major = re.match(r"\d+", version).group()  # leading digits in 17.0, 17rc1
+    return int(major)