test: eliminate for...in loops in test_irc_utils suite

Using `pytest.mark.parametrize()` instead. Two test cases become 12.

Note: Yes, it is possible to have pytest treat each tuple generated by
`itertools.permutations()` as a single argument. Doing so yields useless
generated test-case names like `test_safe[seq0]`, though. Using three
separate test parameters of simple types (`str` or `bytes`) yields more
informative names like `test_safe[\n-\r-\x00]`.

test/irc/test_irc_utils.py

@@ -8,21 +8,21 @@
 from sopel.irc import utils
 
 
-def test_safe():
+@pytest.mark.parametrize('s1, s2, s3', permutations(('\n', '\r', '\x00')))
+def test_safe(s1, s2, s3):
     text = 'some text'
-    variants = permutations(('\n', '\r', '\x00'))
-    for variant in variants:
-        seq = ''.join(variant)
-        assert utils.safe(text + seq) == text
-        assert utils.safe(seq + text) == text
-        assert utils.safe('some ' + seq + 'text') == text
-        assert utils.safe(
-            variant[0]
-            + 'some '
-            + variant[1]
-            + 'text'
-            + variant[2]
-        ) == text
+    seq = ''.join((s1, s2, s3))
+
+    assert utils.safe(text + seq) == text
+    assert utils.safe(seq + text) == text
+    assert utils.safe('some ' + seq + 'text') == text
+    assert utils.safe(
+        s1
+        + 'some '
+        + s2
+        + 'text'
+        + s3
+    ) == text
 
 
 def test_safe_empty():
@@ -35,18 +35,18 @@ def test_safe_none():
         utils.safe(None)
 
 
-def test_safe_bytes():
+@pytest.mark.parametrize('b1, b2, b3', permutations((b'\n', b'\r', b'\x00')))
+def test_safe_bytes(b1, b2, b3):
     text = b'some text'
-    variants = permutations((b'\n', b'\r', b'\x00'))
-    for variant in variants:
-        seq = b''.join(variant)
-        assert utils.safe(text + seq) == text.decode('utf-8')
-        assert utils.safe(seq + text) == text.decode('utf-8')
-        assert utils.safe(b'some ' + seq + b'text') == text.decode('utf-8')
-        assert utils.safe(
-            variant[0]
-            + b'some '
-            + variant[1]
-            + b'text'
-            + variant[2]
-        ) == text.decode('utf-8')
+    seq = b''.join((b1, b2, b3))
+
+    assert utils.safe(text + seq) == text.decode('utf-8')
+    assert utils.safe(seq + text) == text.decode('utf-8')
+    assert utils.safe(b'some ' + seq + b'text') == text.decode('utf-8')
+    assert utils.safe(
+        b1
+        + b'some '
+        + b2
+        + b'text'
+        + b3
+    ) == text.decode('utf-8')