Issue 1:
LibSSH2_jll (7) | started at 2020-12-17T15:29:21.241
From worker 2:	��� Warning: Package LibGit2_jll does not have nghttp2_jll in its dependencies:
From worker 2:	��� - If you have LibGit2_jll checked out for development and have
From worker 2:	��� added nghttp2_jll as a dependency but haven't updated your primary
From worker 2:	��� environment's manifest file, try `Pkg.resolve()`.
From worker 2:	��� - Otherwise you may need to report an issue with LibGit2_jll
From worker 2:	��� Loading nghttp2_jll into LibGit2_jll from project dependency, future warnings for LibGit2_jll are suppressed.
LibSSH2_jll (7) | 1.00 | 0.00 | 0.0 | 0.90 | 1581.01
LibUV_jll (7) | started at 2020-12-17T15:29:22.249
From worker 2:	��� Warning: Module MbedTLS_jll with build ID 45447383554825846 is missing from the cache.
From worker 2:	��� This may mean MbedTLS_jll [c8ffd9c3-330d-5841-b78e-0817d7145fa1] does not support precompilation but is imported by a module that does.
From worker 2:	��� @ Base loading.jl:1003
LibUV_jll (7) | 0.42 | 0.00 | 0.0 | 1.74 | 1581.01
LibUnwind_jll (7) | started at 2020-12-17T15:29:22.670
LibUnwind_jll (7) | 0.28 | 0.00 | 0.0 | 0.29 | 1581.01
Libdl (7) | started at 2020-12-17T15:29:22.951
��� Warning: The call to compilecache failed to create a usable precompiled cache file for LibGit2_jll [e37daf67-58a4-590a-8e99-b0245dd2ffc5]
��� exception = Required dependency MbedTLS_jll [c8ffd9c3-330d-5841-b78e-0817d7145fa1] failed to load from a cache file.
��� @ Base loading.jl:1028
��� Warning: Package LibGit2_jll does not have nghttp2_jll in its dependencies:
��� - If you have LibGit2_jll checked out for development and have
��� added nghttp2_jll as a dependency but haven't updated your primary
��� environment's manifest file, try `Pkg.resolve()`.
��� - Otherwise you may need to report an issue with LibGit2_jll
��� Loading nghttp2_jll into LibGit2_jll from project dependency, future warnings for LibGit2_jll are suppressed.

Seems to be partially a duplicate of #38545 (caused by #27932). Possibly means #38116 needs to be reopened (again)?

https://build.julialang.org/#/builders/4/builds/7130

Issue 2:
Higham and Deadman have published a list of software implementing algorithms for matrix functions, showing that Julia's library for these functions could be improved greatly relative to the state of the art.

The purpose of this issue is to discuss and track the implementation of matrix functions.

From Higham and Deadman's list:

General function evaluations

General matrix function with derivatives of the underlying scalar function available: Schur–Parlett algorithm (Davies and Higham, 2003)

Function of a symmetric or Hermitian matrix by diagonalization

Condition number estimate for general functions: cond(f,A)

matrix function - vector product evaluation: f(A) * b

Specific functions

expm: scaling and squaring algorithm (Al-Mohy and Higham, 2009)

logm: inverse scaling and squaring algorithm (Al-Mohy, Higham, and Relton, 2012,

2013)

sqrtm:

Schur algorithm (Björck and Hammarling, 1983)

real version for real matrices (Higham, 1987)

blocking algorithm for performance improvements (Deadman, Higham, and Ralha, 2013)

A^t for real matrix powers: Schur– Padé algorithm (Higham and Lin, 2013) (#21184)

Matrix unwinding function

Fréchet derivatives

Exponential: scaling and squaring algorithm (Al-Mohy and Higham, 2009)

Logarithm: inverse scaling and squaring algorithm (Al-Mohy, Higham, and Relton, 2013)

General matrix function: complex step algorithm (Al-Mohy and Higham, 2010) or using block 2 × 2 matrix formula.

A^t for real matrix powers: Schur– Padé algorithm (Higham and Lin, 2013)

Miscellaneous functions

inv and det for Tridiagonal and SymTridiagonal matrices (Usmani, 1994) (#5358)