Fix --netrc empty string parsing for Python <=3.10 (#11414)

Ref: https://github.com/python/cpython/commit/15409c720be0503131713e3d3abc1acd0da07378

Closes #11413
Authored by: bashonly, Grub4K

Co-authored-by: Simon Sawicki <contact@grub4k.xyz>

test/testdata/netrc/netrc

@@ -0,0 +1,4 @@
+machine normal_use login user password pass
+machine empty_user login "" password pass
+machine empty_pass login user password ""
+machine both_empty login "" password ""

test/testdata/netrc/print_netrc.py

@@ -0,0 +1,2 @@
+with open('./test/testdata/netrc/netrc', encoding='utf-8') as fp:
+    print(fp.read())