dev-python/nbconvert: Port to py3.9

Signed-off-by: Michał Górny <mgorny@gentoo.org>

dev-python/nbconvert/files/nbconvert-5.6.1-py39.patch

@@ -0,0 +1,27 @@
+diff --git a/nbconvert/filters/strings.py b/nbconvert/filters/strings.py
+index 2673d661..9ae82a13 100755
+--- a/nbconvert/filters/strings.py
++++ b/nbconvert/filters/strings.py
+@@ -19,8 +19,8 @@ except ImportError:
+     from urllib2 import quote  # Py 2
+ 
+ # defusedxml does safe(r) parsing of untrusted XML data
+-from defusedxml import cElementTree as ElementTree
+-from xml.etree.cElementTree import Element
++from defusedxml import ElementTree
++from xml.etree.ElementTree import Element
+ 
+ from ipython_genutils import py3compat
+ 
+diff --git a/nbconvert/preprocessors/svg2pdf.py b/nbconvert/preprocessors/svg2pdf.py
+index aff14d9f..b689b1bc 100644
+--- a/nbconvert/preprocessors/svg2pdf.py
++++ b/nbconvert/preprocessors/svg2pdf.py
+@@ -105,6 +105,6 @@ class SVG2PDFPreprocessor(ConvertFiguresPreprocessor):
+             if os.path.isfile(output_filename):
+                 with open(output_filename, 'rb') as f:
+                     # PDF is a nb supported binary, data type, so base64 encode.
+-                    return base64.encodestring(f.read())
++                    return base64.encodebytes(f.read())
+             else:
+                 raise TypeError("Inkscape svg to pdf conversion failed")

dev-python/nbconvert/nbconvert-5.6.1.ebuild

@@ -3,7 +3,7 @@
 
 EAPI=7
 
-PYTHON_COMPAT=( python3_{6,7} )
+PYTHON_COMPAT=( python3_{6..9} )
 
 inherit distutils-r1
 
@@ -44,6 +44,7 @@ distutils_enable_tests pytest
 
 PATCHES=(
 	"${FILESDIR}"/${P}-inkscape-1.patch
+	"${FILESDIR}"/${P}-py39.patch
 )
 
 src_prepare() {