阅读电子邮件主体时无法编码字符

Question

我在Apache Nifi中使用此代码来读取电子邮件主体（也在Stackoverflow上找到它）：

import email
import mimetypes
from email.parser import Parser
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from java.io import BufferedReader, InputStreamReader
from org.apache.nifi.processors.script import ExecuteScript
from org.apache.nifi.processor.io import InputStreamCallback
from org.apache.nifi.processor.io import StreamCallback

class PyInputStreamCallback(InputStreamCallback):
    _text = None

    def __init__(self):
        pass

    def getText(self) : 
        return self._text

    def process(self, inputStream):
        self._text = IOUtils.toString(inputStream, StandardCharsets.UTF_8)

flowFile = session.get()
if flowFile is not None :
    reader = PyInputStreamCallback()
    session.read(flowFile, reader)

    msg = email.message_from_string(reader.getText())
    body = ""

    if msg.is_multipart():
        for part in msg.walk():
            ctype = part.get_content_type()
            cdispo = str(part.get('Content-Disposition'))

            if ctype == 'text/plain' and 'attachment' not in cdispo:
                body = part.get_payload(decode=True)  # decode
                break
    else:
        body = msg.get_payload(decode=True)

    flowFile = session.putAttribute(flowFile, 'msgbody', body.decode('utf-8', 'ignore'))

    session.transfer(flowFile, ExecuteScript.REL_SUCCESS)

在大多数情况下它都可以，但是有时我会收到错误： unicodeCodeError：'ascii'编解码器无法编码字符u'\ u041a'在位置4784：ordinal不在范围内（128）

我从不使用python并尝试使用.encode修复它（'utf-8'）在此行中：cdispo = str（part.get（'content-disposition'）），但是它没有帮助。也许我认为这个问题出现在这方面。

完整错误：

Processing failed: org.apache.nifi.processor.exception.ProcessException: javax.script.ScriptException: UnicodeEncodeError: 'ascii' codec can't encode character u'\u041a' in position 4784: ordinal not in range(128) in <script> at line number 30
- Caused by: javax.script.ScriptException: UnicodeEncodeError: 'ascii' codec can't encode character u'\u041a' in position 4784: ordinal not in range(128) in <script> at line number 30
- Caused by: Traceback (most recent call last):
  File "<script>", line 30, in <module>
  File "/opt/nifi/nifi-current/work/nar/extensions/nifi-scripting-nar-1.16.3.nar-unpacked/NAR-INF/bundled-dependencies/jython-standalone-2.7.2.jar/Lib/email/__init__$py.class", line 57, in message_from_string
  File "/opt/nifi/nifi-current/work/nar/extensions/nifi-scripting-nar-1.16.3.nar-unpacked/NAR-INF/bundled-dependencies/jython-standalone-2.7.2.jar/Lib/email/parser$py.class", line 82, in parsestr
UnicodeEncodeError: 'ascii' codec can't encode character u'\u041a' in position 4784: ordinal not in range(128)