tests: make a variable for hg binary location in test-check-py3-commands
The number of which calls in here is starting to get silly.
-----BEGIN RSA PRIVATE KEY-----
MIIEpQIBAAKCAQEA6upuVmEs1dTpBWRe4LLM1ARhnMQpI6jaQ8JKzQghMU/3T3n6
Qkimt2HmxuiczvsawAbUPpBAxZbBnKmXbKMiXjtQaO4o4gnyNZVuBgkq2Grc2BRE
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exIKvrpXLfou3s9nCUTs6ekQLi1Tb4PngbhauwIDAQABAoIBABATjQuCSPQ1RuEk
lk2gTt4vkpKM5hfXpWA/uqi/Zq4eP9mDinngyPAB1i5Emv6bNqBvlzTU4GnlQEi9
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jAQa1uTXdDQ6WyuN9LSO3nsNKzal8uucnZxdfFDIHx0MahPlrPfAkqzeKxxfyyRE
jzia24oE+ewE8GHX/TvYnPybCPmBtRwbldA32vx8HbDCvlJanw3dyL98isBa5prr
DsFaDltWzTKdJOIntdTJXRUDwYp7526bUEdGo/1FddbjW6Th8sXiJu91nL3BD/Qk
mW102bECgYEA/zEtKgXjPeV9e3/vvAYU2Bsq8TkmhU6ZiZOQCdPWUNOsyfxibJBk
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RQrsjRNT+cf7HBmKrKd7EknAH2v83ZyPd49BSBiNnmWaqPG2NxCLWpKks20xvRo2
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n9E0PW/wyKI1Gk5U1nHwEJt196kYPzD8QgnwB5MCgYEAloVrHl5aqyex3CaaQU1U
/iMIMUCEeBzkc0GWtDU/NG2mfX1gkKiaiokYj//vgheqUEdzIn1Gy5uRXxZUaT6Z
jwOc7T8jn6vWIALgWZOrlNp7ijjEOISt4EKT4H1HPS9/5gbX+U77LEzHXsdqNZi9
YKNeArc7ip9IWxv/iY3vCAECgYEAgMjOuGqC4Ynpf3x5T17p+PbB/DmPo9xY4ScZ
BEamb2bzpddy0NbfNHJ3JXU0StXms6gqnyO8e/KJhO4gK/37PFO5a7DWMhyFZBIY
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CDD0Gr8CgYEAzwTt62ke3zCFOZ2E6EIR6eM+0Q9+B5zceU8DAZaTTxP4532HnT6/
iHMQvUh0KBE4Rxw3MeSgpe7gKIcMKXubrcDIsEz8vhhOM1xsYIzVEWLtoCLPTaSF
OWQsk98VDt3SgEjb25nOjJ24zZzUVk45OiGUoxfn1Bp6BbJH7IDihCk=
-----END RSA PRIVATE KEY-----