From 48d185fcc42374cd7158c3e28f29ff4b38b03869 Mon Sep 17 00:00:00 2001
From: Karthikeyan Singaravelan <tir.karthi@gmail.com>
Date: Mon, 6 Jul 2020 12:49:31 +0000
Subject: [PATCH 1/2] bpo-41206: Fix EmailMessage.set_content for empty
 content.

---
 Lib/email/contentmanager.py                |  3 +++
 Lib/test/test_email/test_contentmanager.py | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/Lib/email/contentmanager.py b/Lib/email/contentmanager.py
index 2b4b8757f46f62..a0046f880e274e 100644
--- a/Lib/email/contentmanager.py
+++ b/Lib/email/contentmanager.py
@@ -146,6 +146,9 @@ def embedded_body(lines): return linesep.join(lines) + linesep
     def normal_body(lines): return b'\n'.join(lines) + b'\n'
     if cte==None:
         # Use heuristics to decide on the "best" encoding.
+        if not lines:
+            return '7bit', normal_body(lines).decode('ascii')
+
         if max(len(x) for x in lines) <= policy.max_line_length:
             try:
                 return '7bit', normal_body(lines).decode('ascii')
diff --git a/Lib/test/test_email/test_contentmanager.py b/Lib/test/test_email/test_contentmanager.py
index 64dca2d017e629..0eca6d0dfe34d0 100644
--- a/Lib/test/test_email/test_contentmanager.py
+++ b/Lib/test/test_email/test_contentmanager.py
@@ -344,6 +344,19 @@ def test_set_text_plain_long_line_heuristics(self):
         self.assertEqual(m.get_payload(decode=True).decode('utf-8'), content)
         self.assertEqual(m.get_content(), content)
 
+    def test_set_text_plain_empty_content_heuristics(self):
+        m = self._make_message()
+        content = ""
+        raw_data_manager.set_content(m, content)
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="utf-8"
+            Content-Transfer-Encoding: 7bit
+
+
+            """))
+        self.assertEqual(m.get_payload(decode=True).decode('utf-8'), "\n")
+        self.assertEqual(m.get_content(), "\n")
+
     def test_set_text_short_line_minimal_non_ascii_heuristics(self):
         m = self._make_message()
         content = "et là il est monté sur moi et il commence à m'éto.\n"

From 2c041a39ca3176f29956b4e0c88c326cd0bd9aeb Mon Sep 17 00:00:00 2001
From: Karthikeyan Singaravelan <tir.karthi@gmail.com>
Date: Mon, 6 Jul 2020 12:56:26 +0000
Subject: [PATCH 2/2] bpo-41206: Add NEWS entry.

---
 .../next/Library/2020-07-06-12-56-16.bpo-41206.i-tXA-.rst       | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2020-07-06-12-56-16.bpo-41206.i-tXA-.rst

diff --git a/Misc/NEWS.d/next/Library/2020-07-06-12-56-16.bpo-41206.i-tXA-.rst b/Misc/NEWS.d/next/Library/2020-07-06-12-56-16.bpo-41206.i-tXA-.rst
new file mode 100644
index 00000000000000..2f2c018f6b5cc5
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-07-06-12-56-16.bpo-41206.i-tXA-.rst
@@ -0,0 +1,2 @@
+Fix :exc:`ValueError` caused due to empty content passed to
+:meth:`EmailMessage.set_content`.