test: fix python 3.8.4 related regression in T210-raw

It seems (at least in 3.8.4~rc1-1 on Debian) that set_content requires
at least one line.

diff --git a/test/T210-raw.sh b/test/T210-raw.sh
index 85e707d4741c8eb441535ac6a9a1fd7b9496764a..9a8b990c1c3fb4d923b5414a65198986a5412759 100755 (executable)
--- a/test/T210-raw.sh
+++ b/test/T210-raw.sh
@@ -40,7 +40,7 @@ for pow in range(10,21):
     msg['To'] = msg['From']
     msg['Message-Id'] = 'size-{:07d}@notmuch-test-suite'.format(size)
     content = ""
-    msg.set_content("")
+    msg.set_content("\n")
     padding = size - len(bytes(msg))
     lines = []
     while padding > 0: