Hum, later "import ssl" in setup.py also fails. Simplified code:
---
import _ssl
print(_ssl.txt2obj('1.3.6.1.5.5.7.3.1', name=False)) # server OID
---

Error:
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$ ./python x.py 
Uninitialized bytes in MemcmpInterceptorCommon at offset 0 inside [0x701000000032, 8)
==135651==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x49467c in memcmp (/home/vstinner/python/main/python+0x49467c)
    #1 0x7f5546825adc in OBJ_bsearch_ex_ (/lib64/libcrypto.so.1.1+0x14eadc)
    #2 0x7f5546826ff1 in OBJ_obj2nid (/lib64/libcrypto.so.1.1+0x14fff1)
    #3 0x7f554675b434  (/lib64/libcrypto.so.1.1+0x84434)
    #4 0x7f554675b6af in d2i_ASN1_OBJECT (/lib64/libcrypto.so.1.1+0x846af)
    #5 0x7f5546827702 in OBJ_txt2obj (/lib64/libcrypto.so.1.1+0x150702)
    #6 0x7f5546a78c31 in _ssl_txt2obj_impl /home/vstinner/python/main/Modules/_ssl.c:5276:11
    #7 0x7f5546a78c31 in _ssl_txt2obj /home/vstinner/python/main/Modules/clinic/_ssl.c.h:1216:20
    (...)

  Uninitialized value was created by a heap allocation
    #0 0x466642 in __interceptor_malloc (/home/vstinner/python/main/python+0x466642)
    #1 0x7f55468276b3 in OBJ_txt2obj (/lib64/libcrypto.so.1.1+0x1506b3)

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/vstinner/python/main/python+0x49467c) in memcmp
Exiting
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The Python code calls OBJ_txt2obj("1.3.6.1.5.5.7.3.1", 0) in C: the OpenSSL function.