<?xml version="1.0"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"><SOAP-ENV:Body SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"><NS1:GetBlockResponse xmlns:NS1="SysEtranInt"><return xsi:type="xsd:boolean">true</return><Text xsi:type="xsd:string"><?xml version="1.0" encoding="windows-1251"?>
<error>
<errorCode value="4"/>
<errorMessage value="Накладная с ID=1 не найдена или у Вас нет прав доступа к данному документу."/>
<errorStatusCode value="404"/>
</error>
</Text></NS1:GetBlockResponse></SOAP-ENV:Body></SOAP-ENV:Envelope>

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <SOAP-ENV:Body SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
      <NS1:GetBlockResponse xmlns:NS1="SysEtranInt">
         <return xsi:type="xsd:boolean">true</return>
         <Text xsi:type="xsd:string"><?xml version="1.0" encoding="windows-1251"?>
<error>
<errorCode value="4"/>
<errorMessage value="Накладная с ID=1 не найдена или у Вас нет прав доступа к данному документу."/>
<errorStatusCode value="404"/>
</error></Text>
      </NS1:GetBlockResponse>
   </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

body = mk_request(invoiceReturnEmptyCarrige)
doc = xmltodict.parse(body)
print(doc["Envelope"])