RQGIS R package to use QGIS functions is not working: throwing Error, UnicodeEncodeError / Python?

Question

I am currently using R ver. 3.4.1 installed on C:\R\R-3.4.1, installed and loaded Packages: RQGIS, sp, raster. QGIS ver. 2.18.11 installed with OSGeo installer on C:\OSGeo4W64\apps\qgis.

In R I am trying to use the installed RQGIS package to enable QGIS functions via R as shown in the example of the packages GitHub page (https://github.com/jannes-m/RQGIS), I was following.

My environment is set to:

set_env()
$root
[1] "C:\\OSGeo4W64"
$qgis_prefix_path
[1] "C:\\OSGeo4W64\\apps\\qgis"
$python_plugins
[1] "C:\\OSGeo4W64\\apps\\qgis\\python\\plugins"

But unfortunately I always get errors at the following line of code:

library("RQGIS")
find_algorithms(search_term = "([Pp]olygon)(centroid)")

Error in py_str_impl(object) : 
  UnicodeEncodeError: 'ascii' codec can't encode character u'\xfc' in position 77807: ordinal not in range(128)
Error in py_call_impl(callable, dots$args, dots$keywords) : 
  AttributeError: 'file' object has no attribute 'getvalue'

Detailed traceback: 
  File "C:/R/library/reticulate/python\rpytools\output.py", line 14, in end_stdout_capture
    output = sys.stdout.getvalue()

I have already tried reinstalling QGIS, R and all depending packages for a couple of times.

Now I checked Spacedman's suggestions, see below.

For R:

> reticulate::py_config() 
python:         C:\OSGeo4W64\bin\python.exe 
libpython:      C:/OSGeo4W64/bin/python27.dll
pythonhome:     C:\OSGeo4W64\apps\Python27 
version:        2.7.5 (default, May 15 2013, 22:44:16) [MSC v.1500 64 bit (AMD64)] 
Architecture:   64bit 
numpy:          C:\OSGeo4W64\apps\Python27\lib\site-packages\numpy.               
 numpy_version:  1.12.1  
 python versions found:   
 C:\OSGeo4W64\bin\python.exe  
 C:\OSGEO4~1\bin\python.exe   

And in QGIS I entered:

import sys 
sys.executable

'C:\\OSGEO4~1\\bin\\qgis-bin.exe'

Unfortunately I still don't know how to get it up running correctly.