DEV: Adjust string formatting to be able to use mutmut (#1020)

Relates to davidhalter/parso#207

Additionally, make Makefile more consistent

Makefile

@@ -25,7 +25,7 @@ testtype:
 mutation-test:
 	mutmut run
 
-mutmut-results:
+mutation-results:
 	mutmut junitxml --suspicious-policy=ignore --untested-policy=ignore > mutmut-results.xml
 	junit2html mutmut-results.xml mutmut-results.html
 

PyPDF2/generic.py

@@ -565,7 +565,11 @@ def write_to_stream(
             stream.write(b"(")
             for c in bytearr:
                 if not chr(c).isalnum() and c != b" ":
-                    stream.write(b_(rf"\{c:0>3o}"))
+                    # This:
+                    #   stream.write(b_(rf"\{c:0>3o}"))
+                    # gives
+                    #   https://github.com/davidhalter/parso/issues/207
+                    stream.write(b_("\\%03o" % c))
                 else:
                     stream.write(b_(chr(c)))
             stream.write(b")")

mutmut-test.sh

@@ -1,2 +1,3 @@
 #!/bin/bash -e
 pytest -x
+mypy PyPDF2 --show-error-codes --disallow-untyped-defs --disallow-incomplete-defs --ignore-missing-imports

tests/test_writer.py

@@ -291,6 +291,7 @@ def test_encrypt(use_128bit):
 
     reader = PdfReader(tmp_filename, password="userpwd")
     new_text = reader.pages[0].extract_text()
+    assert reader.metadata.get("/Producer") == "PyPDF2"
 
     assert new_text == orig_text